With Lehigh leading 50-49, the Mountain Hawks Tim Kempton pulled down a defensive rebound and was fouled by Franz Rassman with 22 seconds left. But Kempton missed the front end of his 1-and-1 setting up Walker's game-winning heroics on Loyola's final possession.
Lehigh had one final shot with two seconds remaining to win it, but Tyler Jenkins jumper misfired.
The Greyhounds (4-10, 3-0 Patriot League) had trailed 29-18 at the half, but outscored Lehigh 17-6 over the first eight minutes of the second period to tie the score at 35.
Jarred Jones finished with 10 points and 12 rebounds for Loyola.
Kempton and Kyle Leufroy each had 10 points to lead the Mountain Hawks (3-11, 1-2).
The Greyhounds have won three straight to open conference play.