De Grandhomme will make his Hampshire debut in the county’s seventh South group match against Somerset at Taunton (6.30pm). He will replace Kyle Abbott as the second overseas player, alongside Australian opening bat D’Arcy Short.
Lining up against de Grandhomme will be Conway, who makes his debut for the home side.
Conway will no doubt bat somewhere in the Somerset top four, while de Grandhomme is expected to figure in the Hampshire middle order.
Hampshire are in desperate need of victories if they are to finish in the top four and qualify for their first quarter final since 2017.
At present, they have won just one of their opening six matches with three defeats and two abandonments.
De Grandhomme, 34, could well provide the explosive middle order batting the side have generally lacked - apart from when they hit 215 against Middlesex at Radlett (and still lost).
In his 201 T20 matches, de Grandhomme boasts 3,353 runs at 24.29 with a stunning strike rate of 161.20.
Only West Indian all-rounder Andre Russell (169.45) has a higher strike rate among players with more than 1,000 T20 runs.
Hampshire skipper James Vince had a perfect view of de Grandhomme’s last T20 international half-century, as he was on the receiving end of it.
Batting at No 4, he won the man of the match award for hitting 55 off 35 balls as the Kiwis defeated England at Nelson in November 2019 - the same match in which Vince (49) top scored for England.
Prior to that, de Grandhomme had struck 50 off 28 balls against India February 2019, with one four and four sixes
His T20 international strike rate of 143.23 is bettered by only one England player - Dawid Malan (144.31) - and is actually better than that recorded by West Indian master blaster Chris Gayle (148.81)
The Hampshire stint will be de Grandhomme’s third season of T20 Blast action, having appeared for Warwickshire in both 2017 and 2018.
Hampshire supporters will be hoping for some of the explosive hitting he produced for the Bears.
In his first year at Edgbaston, he struck 322 runs in 15 innings with a strike rate of 170.37 - the fourth highest rate of anyone who made 10 or more visits to the crease during that tournament.
His top score was an unbeaten 65 off 28 balls against Derbyshire with five sixes and five fours.
He also took five wickets, but they were at a costly 69.6.
De Grandhomme produced more fireworks in 2018; batting at No 5, he smote an undefeated 63 off 33 balls against Durham with five sixes and four fours.
There were another five sixes in his 49 not out off 28 balls against Nottinghamshire at Edgbaston.
Conway, 29, boasts a highly impressive 44.35 from 89 T20 innings.
For his country, he averages 59.12 after 11 innings - including an unbeaten 99 against Australia in February.
The following month he won two man of the match awards playing for his country against Bangladesh in the space of three days.
First, he hit 126 in an ODI and then an unbeaten 92 in a T20 match.
In all, since making his international debut in a T20 match last November, the South African-born Conway also averages 63.16 in Test cricket - following 200 on his debut at Lord’s last month - and 75.00 in ODIs.
Somerset are looking for their third straight Blast victory after wins against group leaders Kent and Surrey. In the latter game James Hildreth, who opened alongside England international Tom Banton, struck an unbeaten 72.
In addition to those two, and Conway, Somerset have a few big hitters they could call on – Will Smeed hit 42 off 29 balls against Surrey while Ben Green and Lewis Gregory can provide lower order boundaries.
Conway, meanwhile, is no stranger to English conditions, or to Taunton for that matter; he has previously spent two seasons (2015/2016) playing for Vauxhall Mallards in the East Anglian League, and a year (2017) turning out for Nelson in the Lancashire League.
Back in 2010, he also spent a summer playing for Taunton Deane in the West of England Premier League. Over a decade later, he is back in the town again - but with a much higher profile.