The Bhoys prepared for their Champions League second-leg qualifier against Helsingborgs with a comfortable win over the Highlands side to secure all three points
Victor Wanyama and Charlie Mulgrew also scored as the SPL champions prepare for their Champions league qualifier against Helsingborg in midweek, while Ross Draper nicked two late consolation efforts for the Highlands side.
Neil Lennon was forced into making vast changes from last Tuesday's game against the Swedes, with Kelvin Wilson, Wanyama, Mikael Lustig, Paddy McCourt, Filip Twardzik and Watt all coming in for Joe Ledley, Thomas Rogne, Beram Kayal, Scott Brown, Georgios Samaras and Kris Commons.
Just like in their midweek exploits, the Scottish champions got themselves into the lead early on, Caley Thistle keeper Ryan Esson saved a Gary Hooper strike, putting it out for a corner, which Adam Matthews swung in from the right for Wanyama to rise highest and head the ball into the net.
The home side eventually got into the game just after the quarter of an hour mark as Aaron Doran let fly with a strike from just outside the area, which Fraser Forster had to get down well to in order to deflect the ball away for a corner.
Midway through the first half the visitors doubled their advantage as their broke from their own half with Wanyama finding Twardzik on the halfway line, who then found Watt racing forward and beating Simon King, before curling the ball beyond Esson from the edge of the box.
Caley Thistle almost got a goal baack straight away as Shane Sutherland went down the left wing, finding Doran, who then crossed into the penalty area for Andrew Shinnie, but the former Rangers youngster could only put his chance wide of goal.
The Parkhead outfit continued their dominance just before the break, with Hooper finding Watt on the right wing and his cross into the box in search of McCourt was played out by the Caley Thistle defence for a corner.
Celtic started the second half the exact same way they did the first, with Matthews playing a free-kick to Mulgrew, who powered a strike beyond the helpless Esson to give the SPL champions their third of the game.
The visitors continued to look for goals, with Watt taking the ball into the box before searching out strike partner Hooper, but the English frontman’s effort was saved by Esson and eventually cleared from danger.
Watt then tried his luck as he got the ball on the left hand side of the box and after he beat Esson, tried a strike from an acute angle again, but he found the same result as previously as his effort went out of play for a goal kick.
The home side were finding it extremely hard just to get a strike on goal, but when they did; Josh Meekings found his chance from just outside the area easily held by Forster in the Hoops goal.
Celtic then got their fourth of the game as Emilio Izaguirre raced down the left wing before crossing to the back post to Matthews, but he couldn’t convert the chance and eventually Watt rattled the ball into the net for his second goal of the game.
Watt could have had his hat-trick with less than a quarter of the game left as he received the ball on the edge of the area from Lustig, but his curling strike was eventually beaten away by Esson.
With less than 10 minutes to go the home side got a goal back as Andrew Shinnie found Draper inside the box and the midfielder slotted the ball beyond Forster to give the Highland side a crumb of comfort.
They could have had a second goal minutes later as Billy McKay played in Graeme Morrison, but unfortunately for Caley Thistle his strike went well wide.
The home side did get a second with less than five minutes left as substitute Connor Pepper played a ball over the Celtic defence for Draper, his first effort was saved by Forster, but he drilled the rebound to reduce the deficit.
Celtic managed to hold out, not losing any more goals and departed the Highlands with all three points before their crucial Champions League fixture with Helsingborgs.