The eight-division world champion cranked into serious preparations for the May 2 fight after flying in for his training camp from his native Philippines.
On Monday, Pacquiao ran two miles (3.2 km) and shadow-boxed for two rounds, followed by abdominal work and breakfast of steamed rice, scrambled egg, fish and chicken broth.
Then he napped until noon and had lunch before heading to trainer Freddie Roach’s Wild Card Gym, which is strictly off-limits to fans and media during Pacquiao’s sessions.
“I will prepare hard for this fight to give the boxing fans the kind of entertainment they want. This is what I consider the real fight of my life,” said Pacquiao, 36.
Pacquiao (57-5 with two drawn and 38 knock-outs) will face Mayweather (47-0 with 27 knock-outs) in Las Vegas in a fight long craved by boxing fans.
Reports say they will split about $200 million from the welterweight clash between two men considered the best “pound-for-pound” boxers of their generation.
Pacquiao has plunged into training after arriving from the Philippines, where his distractions include playing professional basketball and a seat in the national congress.
He apologised for ducking a crowd of journalists at LA airport after immigration officials whisked him out of a back door on Saturday.
“The head of the immigration in LA led us to the backdoor. So I was not aware that many journalists were already waiting for us outside,” Pacquiao said.
“My heartfelt apology to all of them.”
The devout Christian attended a Bible service on Sunday before beginning his training in earnest the following morning.
Pacquiao’s preparations are under way without Roach, who is in Macau for Chinese fighter Zou Shiming’s world title shot on Saturday.
Conditioning coach Justin Fortune and assistant trainers Buboy Fernandez and Flash Fernandez are present, along with others including Pacquiao’s younger brother Bobby.