Northumberland went ahead after seven minutes with a try by fly-half Will Muir.
Evan Stewart tied up the scores at 5-5 with a pushover try,
Lancashire assumed the lead on 20 minutes as try-scorer Mark Goodman (Sedgley Park) latched on to a neatly-slipped pass by Fylde centre Connor Wilkinson.
The pushover ploy worked again for Lancashire after 37 minutes as the home pack shoved their counterparts backwards in relentless style before Rossendale lock Reece Tomlinson got the final touch to claim the try.
In the ninth minute of added-on time, Fylde's Matt Lamprey scored Lancshire's fourth try, yet again from a pushover.. Team-mate Greg Smith added the conversion,.
Earlier, Lancashire women scored a 51-10 win over Northumberland at the Ansdell ground to maintain their 100 per cent record in the competition.