He began his career in entertainment doing blackface banjo routines in circuses and dime shows, and by 1843 he was well known in New York City.

Whitlock claimed to have met America's pre-eminent banjoist, Joel Sweeney, in 1838 and to have taken some banjo lessons from him.

By 1840, Whitlock was performing circuses, museums, and variety shows and had taken the epithet "King of Banjo players, and the Emperor of Extravaganza Singers".

This playbill, written in the stereotyped African American Vernacular English that characterized blackface entertainment, describes Whitlock's basic act: Now dat Massa Whitlock plays so partic'lar combustious, and will sing dat 'fecting song of Jinny git your Hoe Cake done!

He would "quietly steal off to some negro hut to hear the darkeys sing and see them dance, taking with him a jug of whiskey to make them all the merrier.

[6] Whitlock also did a "Locomotive Lecture", a predecessor to the stump speech, wherein he feigned a complete lack of knowledge about steam engines and the railroad.

On July 28, 1845, Whitlock joined Emmett, Jerry Bryant's Minstrels, Dan Gardner, and Charles "Charlie" White to form the Operatic Brothers and Sisters.