Goals from defender Conor Shaughnessy and Marezi earned Portsmouth their first home win of the season as they beat Cardiff 2-0 on an emotional afternoon at Fratton Park.
The south-coast side paid a poignant pre-match tribute to former goalkeeper Alan Knight, who sadly passed away this week aged 65.
Knight played 801 games for Pompey and also served them as coach and ambassador, and both sets of players lined up around the centre circle for an impeccably-observed minute's silence.
The hosts handed debuts to transfer deadline-day signings Tyrese Shade and Jayden Meghoma.
Cardiff could have opened the scoring after only three minutes when Krystian Bielik headed wide from a Joel Bagan free-kick.
Adrian Segecic had Pompey's first clear chance when his long-range effort was tipped wide by Nathan Trott following an initial poor clearance from the Cardiff goalkeeper.
Portsmouth should have taken the lead after 23 minutes when Marezi headed wide from close range.
A minute later Terry Devlin also failed to keep his header on target from Segecic's low free-kick.
The home side broke the deadlock 14 minutes before half-time when Shaughnessy sent a looping header into the net from new boy Shade's long throw.
Marezi then shanked another presentable chance wide from a tight angle after John Mousinho's men had hit Cardiff on the counter-attack.
Serbian Marezi made amends for his first-half misses by doubling Pompey's lead seven minutes after the re-start.
Segecic picked out Marezi with a pin-point cross and the big striker swept the ball past the helpless Trott.
Marezi thought he had scored his second and Pompey's third when he nodded in Meghoma's cross, only for the goal to be ruled out for offside.
Pompey looked vulnerable defensively, but Cardiff lacked the killer edge to ever look like taking full advantage.
The second from bottom Bluebirds are still waiting for their first Championship win since last season's promotion from League One.
Frustrations boiled over in the final 15 minutes when Cardiff defender Bielik appeared to grab a home fan around the throat.
Pompey almost added a third when Abu Kamara was denied by the crossbar while captain Marlon Pack also had a header from a tight angle blocked.
Cian Ashford almost reduced the deficit in the last minute of the 90 but his shot from the edge of the penalty area proved no match for Pompey goalkeeper Daniel Bielica.
Portsmouth's John Mousinho:
"I'm delighted with the result. It was completely different to the other performances, we didn't necessarily have a huge amount of control in the game, but I thought the first half was pretty good.
"The second half became a bit fractured, Cardiff changed their shape, which caused us a couple of problems.
"Thankfully for us, after we got the second goal, the game broke up a bit as there were quite a few stoppages which probably helped us just to kill the game off.
"You can't be perfect in everything that we do, we strive for that so there are going to be opportunities.
"We have been down in the dumps because of the results, the performances haven't been a million miles off it and there's loads we want to do better, I never ever want to hide behind that.
"We have to make sure we are level when we win games and level when we lose games - and just look for areas to improve because that's going to make us better."
Cardiff's Brian Barry-Murphy:
"It was obviously a very disappointing result.
"We are not happy with the goals we conceded and there are a lot of areas where we can improve.
"We had enough chances to score but were not clinical enough.
"We were not aggressive enough defensively and we always knew it was going to be a very tough test.
"We are confident we can win games at this level, as long as we get the basics right."
