The top-seeded Spaniard had a bye through the first round and was delayed on court for only an hour and nine minutes on Saturday night, a composed performance getting the job done comfortably as Hewitt hit 24 unforced errors to Nadal's eight.
Nadal broke in the first game and again in the fifth before wrapping up the first set after just 27 minutes with a third break.
The second set was closer, with not even a break point in the first seven games, but Hewitt carelessly dropped his serve in the next and Nadal served out ruthlessly for a 6-1 6-3 win.
"I really gave myself a tremendous amount of trouble out there too" - Serena Williams
Third seed Stanislas Wawrinka saw off Daniel Gimeno-Traver 6-0 3-6 6-3 and seventh seed Tomas Berdych accounted for Stephane Robert 7-6 (7/5) 6-1.
But there were several casualties among the seeded players as Jerzy Janowicz, Marin Cilic, Gael Monfils, Gilles Simon, Dmitri Tursunov and Vasek Pospisil all fell.
Monfils, the 23rd seed, lost 6-2 7-5 to Guillermo Garcia-Lopez and fellow Frenchman Simon (26) was beaten 7-6 (7/5) 3-6 6-3 by Portugal's Joao Sousa.
Janowicz (19) was dumped out 6-4 6-1 by Roberto Bautista Agut, the in-form Cilic (25) lost 6-2 7-6 (7/5) to Edouard Roger-Vasselin, Denis Istomin beat Tursunov 6-7 (8/10) 6-0 6-3 and Pospisil (27) was beaten 6-7 (5/7) 7-5 6-3 by Aljaz Bedene.
Fourteenth seed Fabio Fognini made it through, beating Lukas Lacko 6-4 6-4, while Alexandr Dolgopolov (22) beat Jarkko Nieminen - who won his first-round match with Bernard Tomic in an ATP Tour record 28 minutes - 6-4 6-2.
Milos Raonic (12) and Nicolas Almagro (18) were also victorious and contributed to an exodus of home players.
Raonic dispatched fellow big server Jack Sock 6-4 7-6 (7/1) and Almagro beat Sam Querrey 6-4 6-4, while Ryan Harrison lost to Benjamin Becker and Donald Young was the casualty of an all-American tie won 6-7 (5/7) 6-3 6-4 by 10th seed John Isner.
Lucky loser Dusan Lajovic beat Yen-Hsun Lu in three sets while in the doubles, Britain's Colin Fleming and Ross Hutchins were beaten by top seeds Bob and Mike Bryan and Jamie Murray and Dominic Inglot, and respective partners John Peers and Treat Huey, also crashed out.
In the women's event, top seed Serena Williams survived a tough battle against France's Caroline Garcia to eventually progress 6-4 4-6 6-4.
Williams came through a first-set tie-break against Yaroslava Shvedova in the previous round and was again not at her best, but came through in two and a half hours.
"Granted, she played great, but I really gave myself a tremendous amount of trouble out there too,” Williams told the WTA website. “I made so many unforced errors, I hit so short... it really isn't the same player. I really just have to do better."
Williams will play Coco Vandeweghe, who upset 16th seed Sam Stosur 5-7 7-5 7-5 in a match which finished at almost 2.30am local time.
Fourth seed Maria Sharapova was also taken to three sets after losing a second-set tie-break, but eventually progressed 6-4 6-7 (7/9) 6-2 after opponent Lucie Safarova had saved six match points to add to two in the previous set.
The Russian said afterwards: "It was one of those days. I had chances but she kept hitting incredible shots, like winners on match point."
Kirsten Flipkens was granted a direct pass through to face Sharapova after opponent Sabine Lisicki dropped out without taking to the court.
Ana Ivanovic and Petra Kvitova will meet in the same quarter of the draw. Ivanovic beat the in-form Flavia Pennetta 6-4 6-3 while Kvitova reversed that scoreline in beating 17-year-old Croatian Donna Vekic.
Fifth seed Angelique Kerber thrashed Tsvetana Pironkova 6-0 6-2 and will face Ekaterina Makarova, a 6-3 2-6 6-4 winner over Sara Errani.