There were 4,019 Pompey fans who made the trip up to Peterborough to watch a clash between two promotion rivals.
And they saw their side emerge triumphant, with Kusini Yengi's finish in the second half enough to secure all three points.
Blues boss John Mousinho said: "It felt like we were at home at times and the noise was relentless, even in the warm-up.
"That was probably the best away atmosphere I've ever experienced – and I played quite a few games!
"So it was great that we were able to reward that support with a fantastic result and a performance to match."
