The girl's mother, Sarah Key-Marer, was seen crying in the courtroom after the verdict was read.
The prosecution said Brown had every intent of murdering his daughter, Lauren Sarene Key, on Nov. 8, 2000. Brown failed to convince his girlfriend to get an abortion, prosecutors said, so he plotted to kill their daughter to get out of paying child support.
Brown has maintained that his daughter's death was an accident, and that Lauren was running around when she slipped and fell 120 feet down the cliff.
This was Brown's third trial. Two previous juries were deadlocked.
The jury for this trial was instructed to consider not only first-degree murder, but also involuntary manslaughter.
Brown was arrested in 2003 and has been held in custody without bail ever since. He will be sentenced on June 19.