Born in Stavanger, Norway, he grew up in a rich merchant family. He was the son of ConsulJens Zetlitz Kielland and great - grandson of Gabriel Schanche Kielland (1760 – 1821). Kielland was the younger brother of Norwegian landscape painter Kitty Lange Kielland, and their mutual interactions were important to shaping both as artists.

His family also included his son, Jens Zetlitz Kielland, (1873 – 1926); uncle Jacob Otto Lange (1833 – 1902), cousin Axel Christian Zetlitz Kielland (1853 – 1924), nephew Jens Zetlitz Monrad Kielland (1866 – 1926), cousin Anders Lange (1904 – 1974) and great nephew Jacob Christie Kielland (1897 – 1972). His great niece Axeliane Christiane Zetlitz Kielland (1916 – 1995) married Agnar Mykle (1915 – 1994).

Despite being born into wealth, he had a sincere affection for the less fortunate, treating his workers well when he was a factory owner. He remained a spokesman for the weak and a critic of society throughout his time as a writer. His best known plays were the satirical comedies Tre Par (1886) and Professoren (1888). He was also well known for his short stories.

Among his most famous works are the novels Gift (1883), Skipper Worse (1882) and Garman & Worse (1880). Gift (published in English as Poison) is the first in a trilogy including Fortuna (1884) and St. Hans Fest (1887). In this trilogy, Kielland satirizes the hypocrisy of Norway's clergy. In Gift, Kielland debates the hunger for Latin which Norwegian teachers had at this period of time. The story has its peak when a young boy called Marius, is lying on his deathbed, repeating Latin grammar.

It has been debated why Kielland ended his career as a writer so early. Some believe that he was so much of a realist that he could not deal with new romantic tendencies in Norwegian literature at the end of the 19th century. A more probable reason is that he chose to focus on his political career. The biography of Alexander L. Kielland by Tor Obrestad opens up thoughts about Kielland dying from obesity. Already from the mid 1880s, Kielland had suffered from shortness of breath, and he could not put his full energy into writing. He had several heart attacks, he constantly gained weight and he couldn't control his great passion for food.

From 1889 to 1890, Kielland worked as a journalist at Stavanger Avis. Kielland virtually stopped writing fiction in 1891 and published only stories which had appeared earlier. In 1891 he was designated the mayor of his hometown, Stavanger, until in 1902 he moved on to Molde as county governor of Møre og Romsdal.