"It's official I'm bleeding black and gold this morning!" wrote Graham in a tweet later confirmed by the Saints in a statement.
No terms were announced but the deal was reportedly worth $40 million over four years, $21 million of it guaranteed.
The sides met a Tuesday deadline to strike a deal after the Saints designated Graham as a "franchise" player, ensuring him one of the NFL's top salaries at his position.
At issue had been exactly what position that was, with the NFL players' union arguing he should be designated a receiver because he spent more time in such alignments rather than the usual tight end spot in the Saints' offensive formations.
An arbitrator ruled in favor of the Saints earlier this month, Graham's undermined in part because he described himself a tight end on his Twitter page earlier in the year.
Graham will make $7.053 million next season as opposed to the $12.3 million he would have made if classified as a receiver.
Graham made 86 receptions for 1,215 yards with a career-high 16 touchdowns last season and over his four-year NFL career, all with the Saints, he has made 301 catches for 3,863 yards with 41 touchdowns over 62 games.