Hammell fired in off the post in the 25th minute at Fir Park to take his tally for the club to three goals in 386 appearances.
Jamie Murphy slotted home after a penetrating run three minutes later and Keith Lasley wrapped up the contest with a glorious strike in the 77th minute.
The hosts played some inventive football with new signings Nicky Law and Michael Higdon both impressing.
Inverness contributed to an entertaining first half and Richie Foran and Greg Tansey both hit the post, but they ran out of ideas after the interval.
With the SPL enjoying its earliest start to a season, scouts from at least 10 English clubs were present at Fir Park with home pair Murphy and Chris Humphrey the likely points of interest.
Tottenham, Wolves, Stoke, West Brom and Birmingham were among those represented and they saw an early burst of pace and imagination from Murphy.
The 21-year-old broke clear following a one-two with Higdon but slipped the ball just wide under pressure from the chasing Inverness defenders.
The hosts stayed on the front foot and Law shot inches wide of the far post following Higdon’s flick on the edge of the box.
Caley Thistle, who had new arrivals Tansey, Gregory Tade, Andrew Shinnie and Tom Aldred in their line-up, had been restricted to occasional and unproductive counter-attacks until the 18th minute when Foran powered a shot off the base of the post from 25 yards.
Foran soon had a much better chance but blazed over with his left foot from 12 yards following Tade’s knockdown.
Motherwell quickly took the lead after Humphrey got to the byline and crossed from the right. Higdon flicked on and Hammell ran on to meet the ball on the half-volley and shoot high in off the near post.
The 29-year-old previously scored for the club against Partick Thistle in 2004, although he did net four goals during an 18-month sabbatical at Southend.
Murphy soon doubled the lead three minutes after a clinical piece of forward play. Law’s pass allowed the former Scotland Under-21 international to run at the Inverness defence and he sprinted between two men before placing the ball into the bottom corner.
Motherwell looked to be heading comfortably into the interval, but Tansey twice came close in the space of a minute.
The former Stockport midfielder curled a 30-yard free-kick off the inside of the post before meeting Tade’s cross with a cushioned volley, which was blocked at close range by Darren Randolph.
Hammell almost added to his tally after a dynamic one-two with Murphy but his shot was blocked by Ryan Esson’s legs.
Law threatened twice early in the second half, Esson palming away a curling effort from 16 yards before the former Rotherham midfielder shot just over from further out.
Motherwell contained their opponents comfortably and Higdon just failed to get enough contact on Murphy’s deflected strike following a break by Humphrey.
Shane Sutherland came on for Shinnie in the 62nd minute as Caley Thistle manager Terry Butcher looked for a spark, but the visitors still struggled to create chances in open play.
They did force openings from set plays midway through the half but Tom Aldred headed wide and Sutherland volleyed well over.
Despite sitting deeper, Motherwell looked dangerous whenever they forayed into the final third.
Murphy fired just wide from a tight angle after Higdon set him racing down the right and Lasley removed any doubt about the result.
The ball broke to the midfielder 20 yards out following a half-cleared corner and he set himself up to thunder the ball into the top corner.
Jonny Hayes shot not far wide from long range for Inverness but they looked a beaten team.