Galecki is a self-admitted motorcycle "nerd," and rides a Harley Davidson Softail Deluxe. Although he never went to college, he has said: "I'm not dead! We should never stop learning. We should never stop absorbing," and so he learned how to play the cello in his early twenties.

Johnny Galecki is more famously known for playing the character of Leonard Hofstadter on The Big Bang Theory. His character Leonard is an experimental physicist with an IQ of 173. Galecki does not actually wear glasses. In The Big Bang Theory, his glasses are only the frame, without lenses. He secretly dated actress Kaley Cuoco for two years.