Hoolahan scored his 13th goal of the season in the first half and then set up Grant Holt with a brilliant piece of vision in the second to settle a keenly contested encounter and Norwich are two home wins short of their all-time club record.
The Canaries found themselves on the back foot in the early stages, with goalkeeper Fraser Forster saving well from Danny Schofield in the opening minute. But they gradually got a foothold in the game and Chris Martin saw a goal disallowed for offside before Hoolahan's opener in the 28th minute.
Defender Jon Otsemobor did well to get past Schofield on the right before delivering an inch-perfect low cross which Hoolahan side-footed home from 10 yards out.
A quiet second half came to life in the 68th minute when Norwich scored their second. After Millwall had casually given away possession, Martin played in the overlapping Hoolahan and he picked out Holt at the back post with a glorious cross which was simply begging to be headed into the back of the net.
Holt's 20th goal of the season knocked the stuffing out of the Lions although substitute Jason Price came close to pulling a goal back late on.