Singer was born in Pittstown, New York, on October 27, 1811. He was the last born child of Adam Singer and his first wife, Ruth Benson. Isaac's father was a German immigrant from Palatine whose surname at birth was Reisinger. Adam Reisinger, a millwright, and his German wife immigrated in 1803. They had eight children, three sons and five daughters; the eldest daughter's name was Elizabeth Singer. When Isaac Singer was 10 years old, his parents divorced. After Adam Singer remarried and moved to Hannibal/Oswego County, Isaac Singer did not get along well with his stepmother, so when he was 12, he went to live with his elder brother in Rochester. Isaac Singer's elder brother had a machine shop, and Isaac went to work there. It was there that Isaac grew to his full height of 6 feet 4 inches and where he first learned the machinist trade that would become the basis of his fame and fortune. However, at this stage, Isaac did not realize this, and he would look for fame and fortune in another profession: acting.

Isaac was married for the first time in 1830, to Catharine Maria Haley. They seem to have lived first in Palmyra, New York, with her parents for a time. By the summer of 1833 Singer worked in Cooperstown, Otsego County, New York, as mechanic. Isaac had two children by Catharine: William, born in 1834, and Lillian, born in 1837. In 1835 he moved with Catharine and their young son William to New York City, working in a press shop. In 1836, he left the city as an agent for a company of players, touring through Baltimore, where he met Mary Ann Sponsler, to whom he proposed marriage (though he did not actually go through with it). He returned with Mary Ann to New York in 1837. That year Isaac had two children born: his wife Catharine gave him Lillian, and Mary Ann gave him a son, Isaac Augustus. His domestic life with Catharine did not prosper after this, but they were not officially divorced until 1860.

After Mary Ann arrived in New York and found out that Singer was already married, he got into trouble with her. To escape the situation he went to Chicago to work for building the Illinois & Michigan Canal. In 1839 Singer obtained his first patent, for a machine to drill rock, selling it for $200,000 to the I&M Canal Building Company. This was more money than he had ever had before, and in the face of financial success, he opted to return to his career as an actor. He went on tour, forming a troupe known as the "Merritt Players", and appearing onstage under the name "Isaac Merritt", with Mary Ann also appearing onstage, calling herself "Mrs. Merritt". The tour lasted about five years.

In 1844 Isaac took a job in shop of Day Brothers for making wooden types for printing trade in Fredericksburg, Ohio, but moved quickly on to Pittsburgh, Pennsylvania in 1846 to set up his own shop for making wood type and signage. Here he developed and patented a "machine for carving wood and metal" on April 10, 1849. At thirty-eight years old, with Mary Ann and eight children, he packed up his family and moved back to New York City, hoping to market his wood-block cutting machine there. He obtained an advance to build a working prototype, and constructed one in the shop of A.B. Taylor & Co. Here he met G.B. Zieber, and he became Singers financier and partner. However not long after the machine was built the steam boiler blew up at the shop, destroying the prototype. Zieber persuaded Singer to make a new start in Boston, a good place of printing trade. In machine shop of Orson C. Phelps they found a show room for the new prototype. Singer went to Boston in 1850 to set up his machine at the Phelps' machine shop. Orders for Singer's wood cutting machine were not, however, forthcoming. Coincidentally Lerow & Blodgett sewing machines were being constructed and repaired in Phelps' machine shop. Phelps asked Singer to look at the sewing machines, which were difficult to use and difficult to produce. Singer noted that the sewing machine would be more reliable if the shuttle moved in a straight line rather than a circle, with a straight rather than a curved needle. Singer was able to obtain US Patent number 8294 on his improvements on August 12, 1851. Singer's prototype sewing machine became the first to work in a practical way.

Singer did not invent the sewing machine, and never claimed to have done so. By 1850, when Singer saw his first sewing machine, it had been "invented" four times. All sewing machines before Walter Hunt's produced a chain stitch, which had the disadvantage of easily unravelling. Hunt's machine produced a lock stitch, as did all subsequent machines including Lerow and Blodgett's, which Singer in turn improved in Phelps's shop. Elias Howe independently developed a sewing machine and obtained a patent on September 10, 1846. War broke out between Howe and Singer, with each claiming patent primacy. Singer set out to discover that Howe's improvements had been reinventions of existing technology, and found one of Hunt's old machines, which indeed created a lock-stitch with a shuttle. Hunt applied in 1853 for a patent, claiming priority to Howe's patent, issued some seven years earlier. A lawsuit, Hunt v. Howe, came to trial in 1854, and was resolved in Howe's favor. Howe then brought suit to stop Singer from selling Singer machines, and protracted litigation ensued.
In 1856, manufacturers Grover & Baker, Singer, Wheeler & Wilson, all accusing the others of patent infringement, met in Albany, New York to pursue their suits. Orlando B. Potter, a lawyer and president of the Grover and Baker Company, proposed that, rather than sue their profits out of existence, they pool their patents. This was the first patent pool, a process which enables production of complicated machines without legal battles over patent rights. They agreed to form the Sewing Machine Combination, but for this to be of any use they had to secure the cooperation of Elias Howe, who still held certain vital uncontested patents which meant he received a royalty on every sewing machine manufactured by any company. Terms were arranged, and Howe joined on. Sewing machines began to be mass produced: I.M. Singer & Co manufactured 2,564 machines in 1856, and 13,000 in 1860 at a new plant on Mott Street in New York. Later a massive plant was built near Elizabeth, New Jersey. Sewing machines had until now been industrial machines, made for garments, shoes, bridles and for tailors, but in 1856 smaller machines began to be marketed for home use. Singer was the first who put a family machine, "The turtle back", on the market. I.M. Singer expanded into the European market, establishing a factory in Clydebank, near Glasgow, controlled by the parent company, becoming one of the first American-based multinational corporations, with agencies in Paris and Rio de Janeiro. Credit for the invention of the sewing machine, so Andrew B. Jack, must go to I.M. Singer on three very important counts: 1. only he used the 10 most important elements for highest capacity and adaptability; 2. his design was a revolution of former attempts; 3. his concept is still today the basis of all sewing machines.

The financial success gave Singer the ability to buy a mansion on Fifth Avenue, into which he moved his second family. In 1860, he divorced Catherine, on the basis of her adultery with Stephen Kent. He continued to live with Mary Ann, until she spotted him driving down Fifth Avenue seated beside one Mary McGonigal, an employee, about whom Mary Ann had well-founded suspicions, for by this time Mary McGonigal had borne Isaac Singer five children. The surname Matthews was used for this family. Mary Ann (still calling herself Mrs. I.M. Singer) had her husband arrested for bigamy. Singer was let out on bond and, disgraced, fled to London in 1862, taking Mary McGonigal with him. In the aftermath, another of Isaac's families was discovered: he had a "wife" Mary Eastwood Walters and daughter Alice Eastwood in Lower Manhattan, who both adopted the surname "Merritt". By 1860, Isaac had fathered and recognized eighteen children (sixteen of them remaining alive), by four women.

With Isaac in London, Mary Ann began setting about securing a financial claim to his assets by filing documents detailing his infidelities, claiming that though she had never been formally married to Isaac, that they were in fact wed under Common Law (by living together for seven months after Isaac had been divorced from his first wife Catherine). Eventually a settlement was made, but no divorce was granted. However, she asserted that she was free to marry, and indeed married John E. Foster. Isaac, meanwhile, had renewed acquaintance with Isabella Eugenie Boyer, a Frenchwoman he had lived with in Paris when he was staying there in 1860. She left her husband, and married Isaac under the name of Isabella Eugenie Sommerville, on June 13, 1863, while she was pregnant.

In 1863, I.M. Singer & Co. was dissolved by mutual consent, with the business continued as "The Singer Manufacturing Company," enabling the reorganization of financial and management responsibilities. Singer no longer actively participated in the firm's day-to-day management, but served as a member of the Board of Trustees (even though he now lived in Europe) and was a major stockholder.

He now began to increase his new family: he would eventually have six children with his wife Isabella. Unable, probably because of Isaac's chequered marital past, to enter New York society, the family emigrated to Paris, never to return to the United States. Fleeing the Franco-Prussian War, they resided first in London, then in Paignton, (near Torquay) on the Devon coast where he built a large house, Oldway Mansion. He brought some of his other children to live there. Nine days after the wedding of his daughter Alice Merritt to William Alonso Paul La Grove, Isaac Singer died of "an affection of the heart and inflammation of the wind-pipe." He was interred in Torquay cemetery.

Singer left an estate of about $14,000,000 and two wills disposing this between his family members, leaving some out for various reasons. Suits followed, with Mary Anne claiming to be the legitimate "Mrs. Singer". In the end Isabella was declared the legal widow. Isabella remarried in 1879 with Dutch musician Victor Reubsaet and settled in Paris. After his death in 1887, she remarried in 1891 with Paul Sohège.