Oldham centre-back Manny Monthe's first goal of the season consigned troubled Harrogate to a sixth straight defeat.
The Latics secured a 1-0 win despite a 79th-minute red card for midfielder Ryan Woods, with the hosts' losing streak having now stretched to the longest during Simon Weaver's 16-and-a-half-year reign as manager.
Earlier, home striker Shawn McCoulsky had missed a gilt-edged opportunity to open the scoring in the fifth minute, wastefully scuffing wide after being sent clear on goal by Jack Muldoon.
Instead, it was the Lancashire outfit who forged ahead in the 23rd minute when Harrogate failed to deal with Jamie Robson's inswinging corner from the right and Monthe swivelled to net from three yards.
The visitors thought they had added a second just past the half-hour mark but Joe Garner's header was ruled out by a contentious offside flag.
After the break, Ellis Taylor was denied an equaliser when his thumping 20-yard strike was brilliantly fingertipped onto the crossbar by Matthew Hudson.
Oldham were then reduced to 10 men when Woods, cautioned 14 minutes earlier for a foul on Muldoon, foolishly received a second yellow card for dissent.
But it proved a fruitless day for the Sulphurites and skipper Warren Burrell, whose 447th appearance equalled Paul Williamson's all-time club record.
Report supplied by PA Media.
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