In their first season at the highest level of the semi-professional game in Wales, Merthyr were crowned Premiership Tier One champions following a dramatic 22-18 final victory over Aberavon.
Jarvis kicked 12 points to add to tries from Richard Carter and Kyle Evans as the Ironmen came out on top at the Talbot Athletic Ground.
He said: “It was nip and tuck right till the end. Aberavon clawed it back, but the boys dug deep and people outside the club don’t understand the culture we are building here.
“Now we’ve topped it off with a win down here. We had a disappointing result against RGC in the Cup and since then we’ve gone unbeaten. We’ve bounced back and this is tremendous for the club.
“To win the title in our first season in the Premiership… I can’t describe how happy we are as a squad and coaching staff.”
Merthyr were playing in Division One East just three years ago, but their Premiership final victory was the crowning glory on their remarkable rise up the divisions.
Now Jarvis wants Merthyr to dominate Welsh semi-professional rugby for the next few seasons.
“It’s great for the boys who were with the club when we were playing down the leagues, but we can’t stop here,” he added.
“We need to build on this now in the next couple of years, keep on improving, and keep on winning trophies. We always back ourselves.
“We knew coming into this game that playing at Aberavon was always going to be tough. They had home advantage, but we came here with great confidence despite it being a tough place to come.
“I played here for two and a half years and I hold this club in great regard, but it was great to come here and get the result.”