A tight match opened up late on, with Matt Macey twice called upon in the dying moments, while substitute Ronan Curtis had two great chances.
But Colby Bishop should have settled it two minutes from time, over to shoot over from eight yards with just Carl Rushworth to beat.
Some encouraging displays, however, and here are our on-the-whistle player ratings...
1. Goal, Portsmouth midfielder Myles Peart-Harris (44) scored, Lincoln City 0-1 Portsmouth during the EFL Sky Bet League 1 match between Lincoln City and Portsmouth at Sincil Bank, Lincoln, United Kingdom on 27 April 2024.
Myles Peart-Harris celebrates opening the scoring against Lincoln. Picture: Jason Brown/ProSportsImages Photo: Jason Brown
2. Will Norris - 6
Too casual with his pass to help gift Lincoln a penalty, then dived to his right to keep out Mandroiu’s awful spot-kick. Overall, the keeper's kicking was unusually shaky. Did well to punch the ball away in the second half from under his bar. Captain for the afternoon. Photo: Jason Brown
3. Joe Rafferty - 7
Out of contract in the summer so potentially his last match, hopefully not. Turned in a characteristic rugged defensive display and the reliable presence in a much-changed team. Photo: Jason Brown
4. Ryley Towler - 8 - MOM
Only his sixth league outing of the season, but replaced Raggett and looked a class act. Comfortable on the ball, fed Sparkes with one excellent pass in the first half. Magnificent tackle on Makama to prevent him scoring after the break. Photo: Jason Brown