Leicester scored five tries through Tom Croft, Ben Youngs, Mathew Tait, Vereniki Goneva and Toby Flood at Welford Road which guarantees them second place behind Saracens and a home semi-final next Saturday.
Irish's tries were scored by Alex Corbisiero, Topsy Ojo and Marland Yarde.
Leicester recalled club captain Geordan Murphy and Italy prop Martin Castrogiovanni and picked all their six members of the British and Irish Lions squad in a match they needed to earn two points from to be certain of a home draw.
Irish, rooted in the bottom half of the table after a difficult season, were captained by former Leicester lock George Skivington.
There was a 24,000 sell-out crowd at sun-drenched Welford Road and Irish started strongly, Ian Humphreys' third-minute penalty reward for a concerted attack.
Leicester, wearing their new strip, drew level thanks to a Flood penalty three minutes later and then hit the visitors with two tries in the space of three minutes.
The first came after Irish inexplicably tried to run the ball out of defence in front of their own posts and got turned over, Croft finishing off a slick handling move in the 14th minute.
Fellow Lion Youngs then handed off England prop Corbisiero before making a 22-metre dash for the line. Flood missed both conversions from the right touchline.
The Irish should have got themselves back in the game in the 26th minute when Jamie Gibson charged down a clearance kick near the Leicester line. Although tackled just short of the try line, the flanker had a man outside him but his pass flew straight into touch.
Irish scrum-half Darren Allinson escaped with a ticking off from the referee after appearing to kick Murphy on the floor and that led to a period of Leicester pressure.
They turned down penalties in the search for more tries and winger Goneva had one chalked off for a forward pass by Murphy.
The game really opened up near the end of the half and Irish were left kicking themselves after a knock-on ruined a chance for winger Marland Yarde.
Tait replaced Leicester centre Anthony Allen at half time and within eight minutes he had got himself on the scoresheet.
Leicester's third try came after an Irish clearance which was taken by winger Niall Morris. The Tigers spread the ball wide, Manu Tuilagi made the all-important break and Tait finished it off, Flood kicking the conversion to make it 20-3.
The visitors, however, struck back immediately with a short range try from a ruck by Corbisiero which was converted by Humphreys.
They then turned defence into attack with a terrific break down the right from their own 22 and ran the ball back to Leicester's posts after Morris' poor clearance.
They failed to capitalise and Leicester blasted down to the other end and scored their fourth try to earn a bonus point, Goneva sprinting over from Flood's one handed flick-on after great work by lock Graham Kitchener. Flood kicked the conversion to make it 27-10.
Flood then made it 32-10 with a try and conversion before Irish wing Ojo won the race to a chip from replacement Shane Geraghty for the visitors' second try. Humphreys missed the conversion.
They could have had another a minute later when Ojo burst through to the 22 but failed to find a man in support, but fellow winger Yarde scored a fabulous solo effort with just over a minute left.
- Sports & Recreation
- Marland Yarde
- Mathew Tait
- Geordan Murphy