Lorent Tolaj joined Bristol City from Plymouth in July
Bristol City picked up their first win under Michael Skubala as they saw off Portsmouth in the Championship.
Summer signing Lorent Tolaj put the hosts in front at Ashton Gate, superbly finishing Jed Wallace's cross first-time.
Captain Jason Knight doubled the lead after the break as he headed in Rio Cardines' corner.
Pompey were restricted to half-chances by some excellent City defending but got a consolation deep in stoppage time through Marezi's penalty.
Skubala's start to his tenure in the West Country following his arrival from Lincoln City had been underwhelming.
Following a home defeat by League Two Walsall in the Carabao Cup to begin the campaign, his side then lost to Millwall and conceded a 95th-minute leveller against Birmingham in the Championship.
Swiss striker Tolaj showed the quality that had helped him score 22 goals last season with a lovely hooked finish that gave Pompey goalkeeper Nicolas Schmid no chance.
Knight's powerful header gave City a cushion and despite Portsmouth pulling one back when they were awarded a spot kick in the 95th minute when Marezi went down in the box, they had no time to find a leveller.
Both sides are back in action on Tuesday when Bristol City visit struggling Preston and Portsmouth host Derby.
'Some excellent performances' - Bristol City reaction
Bristol City boss Michael Skubala told BBC Radio Bristol:
"I thought first half in particular we were very good.
"The second goal was a goal we've been working on in training. There were some good performances out there, it's excellent to get the win.
"At the end, I'm not sure it needed to go to 2-1, but the most important thing is to get the three points."
Skubala: "It's always good to get 3 points"
'So many aspects we need to improve' - Pompey reaction
Portsmouth boss John Mousinho told BBC Radio Solent:
"It was a really frustrating afternoon.
"Every goal conceded is frustrating for us because we went away from what we've been trying to work on over the past six to eight weeks.
"The performance wasn't disastrous, we've been here the past two years and been way off it.
"We were a lot closer but I still think there's so many aspects of our game that we need to improve."
John Mousinho: 'We need to improve quickly'
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