The South Australian, who had an unsuccessful season with Yorkshire in 1999, looked in majestic form as he completed his maiden Nottinghamshire hundred from 178 balls - hitting 17 boundaries along the way.
By the time he was beaten in the flight by off spinner Michael Gough and was smartly stumped by Andrew Pratt, he had added four more fours. Nottinghamshire finished the day on 344 for six.
He offered only one chance during more than five hours at the crease - a sharp return catch that Paul Collingwood found too hot to hold - but then added further insult by belting the next two balls for fours.
"It's nice to get runs straight away wherever you play as it takes the pressure off a bit and hopefully will set me up for the rest of the season. Strangely, I did not feel I batted all that well but I was staying balanced, playing down the right lines, leaving the right balls and the end result was good," Blewett, who played the last of his 46 Tests for Australia in March last year against New Zealand, said.
Blewett, 29, arrived in Nottinghamshire at the peak of his game having topped the scoring charts in the Australian domestic season. Not since Fred Stocks in 1946 has a Nottinghamshire player made his debut in the County Championship and registered a triple figure score.
At New Road, Zimbabwe batsman Murray Goodwin almost equalled Blewett's feat, scoring 94 on his Championship debut for Sussex against Worcestershire.
The 28-year-old cracked 17 fours off 116 balls to help lift his side to 192 for five by the close as this Second Division fixture finally got under way after two days of rain.
Worcestershire's Australia pace bowler Andy Bichel, overlooked for the Ashes tour, finished the day with three for 46.
In the First Division Somerset's England opening batsman Marcus Trescothick made an impressive 147 off 227 balls including a six and 23 fours to help his side to 307 for three for at the close, a deficit of 46 against Glamorgan at Cardiff.
Essex captain and former England all-rounder Ronnie Irani took five for 43 as Northamptonshire were bowled out for 150 at Chelmsford. Australia star Sturat Law then made 58 as Essex closed at 257 for eight, a lead of 313.
At Canterbury, Kent opener Robert Key continued his impressive start to the season making 97 not out as the home side battled to avoid defeat against Yorkshire
Kent was 192 for five in their second innings at the close, a lead of 49. Play in the other First Division match between Lancashire, last season's runners-up and reigning champions Surrey was washed out for a third straight day.
In the Second Division, England chairman of selectors David Graveney watched former England left-arm spinners Phil Tufnell and Richard Illingworth take four wickets apiece at Derby.
First Derbyshire made 198 (Tufnell four for 42) before Illingworth (four for 37) helped reduce Middlesex to 146 for five at the close.