Cheltenham showed no signs of their exertions at Sunderland as they secured all three points with all the goals coming in the first half. And while Northampton had chances to get back into the contest they didn't seriously threaten the Robins' goal.
Northampton had three good early chances with Jason Crowe, Ian Taylor and Petr Mikolanda all going close before Cheltenham got their noses in front in the 20th minute.
A long clearance from keeper Shane Higgs caused problems for his opposite number Lee Harper, who failed to hold on to the ball under pressure from Odejayi and the Cheltenham striker gratefully accepted the chance to find an empty net.
Taylor went close with a shot on the turn before he put Northampton back on level terms on the half hour mark. A neat five-man move ended with Taylor turning well just inside the area to find the top corner with a curling shot.
Northampton had chances to establish a first half lead with Scott McGleish and Mikolanda heading over while Odejayi should have done better with a header a minute before the break.
But he made amends a minute into first half stoppage time when a left-wing cross from David Bird found the unmarked Odejayi who headed home from six yards.
Northampton, despite lacking fluency, had chances to earn at least a point.
McGleish twice went close with far post headers while Taylor saw another header come back off the post with McGleish foiled from the rebound by Higgs who claimed the ball at the second attempt to earn Cheltenham three precious points.