Theodor Leschetizky was born on the estate of the family of Count Potocki in Łańcut. His father was a gifted pianist and music teacher of Viennese birth. His mother Therèse (von) Ulmann was a gifted singer of German origin. Leschetizky's father gave him his first piano lessons and then took him to Vienna to study with Czerny. At age eleven he performed a Czerny piano concerto in Lemberg (near Łańcut), with Franz Xaver Wolfgang Mozart (the son of Wolfgang Amadeus Mozart) conducting. At the age of fourteen, he started to tutor his first pupils. By the age of eighteen he was a well known virtuoso in Vienna and beyond. His composition teacher was Simon Sechter, subsequently the teacher of Anton Bruckner.

At the invitation of his friend Anton Rubinstein he went to St. Petersburg to teach in the court of the Grand Duchess Helen. Remaining there from 1852 to 1877, he was one of the founders of the St. Petersburg Conservatory of Music in 1862. While in Russia he married one of his most famous pupils, Anna Yesipova (the second of his four wives), and had two children (one of them Robert Leschetizky).

In 1878 he returned to Vienna and began teaching there, creating one of the most eminent private piano studios in history, besides Franz Liszt in Weimar. He taught thousands of students, in the Weimarerstraße (formerly the Carl Ludwigstraße) XIX. Bezirk Wien, Vienna. They came from all over the world, many from the United States. Leschetizky taught until the age of 85, leaving for Dresden in 1915, where he died that year.

He was survived by a son, Robert (Dresden), whose family returned to Bad Ischl after his death. His descendants still live in Bad Ischl and there is a Leschetizky Villa at the Leschetizky Straβe, the summer resort, where Theodor Leschetizky often vacationed with his friend Johannes Brahms.

Leschetizky had a granddaughter, Ilse Leschetizky (1910 - 1997), who was a distinguished pianist and teacher. One of her daughters, Margret Tautschnig, continues the Leschetizky tradition with the Leschetizky Verein Ősterreich in Bad Ischl. This organisation was co-founded by the Belgian pianist Peter Ritzen.

Among his celebrated Vorbereiter (assistants who prepared students to play for him) were Katherine Goodson, Annette Hullah, Marie Prentner, and Malwine Brée, author of The Leschetizky Method (a title which he approved, while stating that there "was no method!"). The list of virtuoso concert artists he trained includes Anna Yesipova, Ignaz Friedman, Ignacy Jan Paderewski, Artur Schnabel, Mark Hambourg, Alexander Brailowsky, Benno Moiseiwitsch, and Mieczysław Horszowski.

Perhaps the secret of his successful teaching was that he worked with each student's personality and technical abilities in an individual way. His famous weekly classes provided his students the opportunity to try out their pieces prior to public performances before a discerning audience of their fellow students and invited guests.

A humourous probable allusion to Leschetizky occurs in the "Stella in Oxford" Chapter (Book Three, Chapter 10) of Compton Mackenzie's 1913 - 1914 novel Sinister Street, where there is mentioned a notable teacher of the piano in Vienna "with a perfectly impossible name beginning with L".

Until his death, Leschetizky espoused a philosophy of music making and enjoying life to the fullest, captured in one of his most famous sayings (translated from the German):

"No art without life, no life without art."

Theodor Leschetizky possessed a distinct talent for composition. He wrote over one hundred characteristic piano pieces, two operas: Die Bruder von San Marco and Die Erste Falte, thirteen songs, and a one - movement piano concerto. Opus numbers were given to 49 works.

Although his piano pieces are primarily smaller works in the genre of salon music, they display an expressive lyric gift while exploiting the piano's capabilities to great effect. Most of Leschetizky's music has been out of print since the early twentieth century, with the exception of the Andante Finale, Op. 13 (a paraphrase for piano left hand on the famous sextet from the opera Lucia di Lammermoor by Donizetti); and Les deux alouettes, Op. 2, No. 1.