Ireland, who had five of their starting XI making their debuts, fell behind to Michael Eneramo's opener before Keane levelled before the interval in Friday night's international friendly at Craven Cottage.
It means Giovanni Trapattoni's men head to Bulgaria without breaking their momentum after going unbeaten in qualifiers so far.
Trapattoni also has options now after Kevin Foley, Sean St Ledger, Eddie Nolan, Liam Lawrence and Leon Best were among the debutants starting. Keiren Westwood then came on at the break for his first appearance.
The Italian wanted to look at these players ahead of the trip to Sofia, where a win will mean a huge stride towards at least a play-off to reach South Africa next year.
It was Foley, however, who was at fault for Eneramo's goal on the half-hour mark.
Nigeria had hardly threatened seriously, apart from a speculative 40-yard free-kick from Sone Aluko that Shay Given tipped over, but they were ahead slightly against the run of play.
Femi Olubayo, on the right, fizzed in a cross first time which Foley should have cleared but Eneramo was a fraction quicker, wrapped his foot around the ball and his finish fizzed past Given.
That sprung Ireland into action, with three debutants combining shortly after. Lawrence swung over a free-kick that St Ledger headed back into the danger area, with Best's finish striking the post.
Best's partnership with Keane was showing signs of promise, with the Coventry striker latching on to balls through and getting close before he struck the woodwork.
Best, however, did not have a part to play in Keane's leveller. It was an eye-pleasing move, starting from Liam Miller's flick around a defender to Keith Andrews.
Andrews split the Nigeria defence with his pass, then Ireland's skipper and all-time top scorer did the rest, taking the ball past goalkeeper Austin Ejide and tucking away his finish.
Westwood came on for his debut at half-time, with Trapattoni replacing three of his senior players. Given, Keane and Damien Duff made way, with Aiden McGeady and Shane Long the other players introduced.
Long almost grabbed a goal seven minutes after the interval when Best chased down Ejide and forced the goalkeeper into a poor clearance. Long measured his lob but Ejide was back in time to palm away.
McGeady tried his luck from long range with 20 minutes remaining but his effort swerved wide, then Foley was replaced by Paul McShane.
The crowd started a Mexican wave with plenty of time remaining, a sign of the friendly heading towards a draw.
Nigeria themselves have a World Cup qualifier against Kenya coming up and players such as Obafemi Martins did not feature, while Joseph Yobo and Mikel John Obi were preparing for the FA Cup final with their clubs.
Nsofor Obinna came off the bench for the Africans and went just wide with a drive.