Point at Grimsby not enough for Plymouth
Plymouth let the League Two title slip from their grasp as they were held to a 1-1 draw at Grimsby.
Jimmy Spencer had given the Pilgrims hope when he equalised after Shaun Pearson's early goal, but a point was not enough to retain top spot due to Portsmouth winning.
Grimsby made a blistering start to the game as they opened the scoring inside the first minute, with Pearson smashing the ball into the roof of the net after Luke McCormick failed to deal with Danny Andrew's corner.
Graham Carey tested James McKeown from a narrow angle, before the goalkeeper again denied the midfielder from a free-kick on the edge of the box.
Plymouth had McCormick to thank as he produced a fine save to prevent Sam Jones from doubling the hosts' lead after his defence failed to handle a bouncing ball.
With the title on the line, the visitors came out for the second half firing, but Carey was once again denied by McKeown as the Grimsby keeper tipped away the midfielder's strike.
Argyle levelled in the 61st minute when Spencer was put through on goal just seconds after coming off the bench, and he calmly slotted the ball home to give his side hope of snatching the title back.
They were frustrated by an inspired McKeown in their search for a winner though as Portsmouth were crowned champions.