Celtic are now two points behind second-placed AC Milan in Group H with three fixtures remaining, and Lennon has applauded the significant effort of his injury-depleted squad to put them in that position.
"I said they would give us problems and our squad is stretched, so that's a fantastic win for us and a monumental effort from the players tonight," Lennon told reporters.
"We needed our goalkeeper to make a great save just before we got the second goal, but I felt that in the second half tonight we were a lot better. We didn't keep the ball well enough for my liking in the first half but we grew into the game.
"It leaves us in a very good position. We will have to get a result in Amsterdam and that is going to be very difficult on tonight's evidence but it is not beyond us."
The Scottish outfit host AC Milan after the reverse fixture with Ajax in a fortnight's time, and then finish their group stage campaign with a visit to Barcelona.