The 27-year-old told the judge on Thursday he knows he was wrong and entered the guilty plea because "it's the right thing to do."
He faces up to 25 years in prison when he's sentenced in December.
Prosecutors say analyst Damilare Sonoiki fed Kendricks confidential information on four companies about deals that sent their stock prices soaring.
They say at the end of the two-year scheme, Kendricks made about $1.2 million.
Sonoiki's lawyer tells the Philadelphia Inquirer that his client also would plead guilty, but no date is set.
Copyright 2018 by The Associated Press.