First half tries from Brad Graham, Paul Sykes and Connor Davies, all converted by Sykes, put the Rams 18-4 ahead at the break.
A Tommy Brierley try for Oldham in the second half narrowed the deficit but the Rams held firm to secure a 12th league victory of the season and go five points clear at the top of the table.
It was a history-making night for Sykes as he added a penalty late on to break the 1,000-point barrier for the Rams, becoming only the second player to do so in the summer era of rugby league.
Speaking to the Dewsbury Rams website after the match, head coach Liam Finn said: “I’m really proud of what the lads did out there tonight.
"Obviously we knew it was going to be a tough game. Oldham are a good team and probably as good as anyone in the competition so we knew that we were going to have to be on it.
“It wasn’t pretty at times, at certain points we just had to be methodical and just grind the sets out and we got through it and came away with the win.”
Here are 15 photos from last night’s match, courtesy of TCF Photography.