Hosts Newport dominated for long periods at Rodney Parade on Monday, but it was Cambridge who took the lead just after half-time through substitute Luke Chadwick.
Cambridge will have been sensing revenge for the 6-2 hammering they took on their visit to south Wales two years ago, although their hopes were dented when Chadwick was withdrawn just seven minutes after his goal due to a hamstring injury.
Injuries played a pivotal role in the outcome of the game, with Cambridge reduced to 10 men when midfielder Liam Hughes came off with an arm problem in the 87th minute after manager Richard Money had already made three substitutions.
And the depleted visitors could not hold firm as midfielder Willmott came back to haunt his former club by securing a share of the spoils for Justin Edinburgh's men.
The result sees Newport move up one place to 19th in the table, while Cambridge sit 11th.
