The visitors were behind with just three minutes on the clock when Rhys Hanbury crossed the whitewash, but they hit back with tries of their own in a tightly-contested battle at the Select Security Stadium.
Lance Hohaia found the tryline with 14 minutes remaining to ensure a tense finale, but Macgraff Leuluai made sure of the points by adding try number seven late on for Widnes.
Logan Tomkins cancelled out Kevin Sinfield's opening try on the half-hour mark, but Rhinos crossed over five more times in the second half to make sure of the points, with Tom Briscoe rounding off the scoring in the dying seconds.
It took just five minutes for the Cherry & Whites to get up-and-running courtesy of Blake Green's try, before he and Anthony Gelling each completed a double in Wigan's 15-try romp over their struggling opponents.
Michael Monaghan managed to pull the visitors right into the contest when he crossed over on 22 minutes, but Castleford showed their strength to win the match in a straight-forward fashion.
Mason Caton-Brown added a consolation try for Broncos just short of the hour-mark, but they remain in trouble, second from bottom in the table.
Jodie Broughton opened up the scoring inside eight minutes for the hosts, while two tries after the interval from Jason Chan and Shaun Lunt ensured that they took the points to lift them up to seventh in the table.
Results in full: Huddersfield Giants 36-16 Wakefield Trinity Wildcats, Hull FC 40-4 London Broncos, Leeds Rhinos 32-4 Salford Red Devils, Widnes Vikings 40-26 St Helens, Wigan Warriors 84-6 Bradford Bulls, Castleford Tigers 40-6 Warrington Wolves