The 19-year-old overcame a nervy start on her Centre Court debut to beat Alison van Uytvanck 6-4 6-4.
Backed by an enthusiastic home crowd, the US Open champion showed no sign of the side injury that hurt her build-up.
“I really felt like today I made that court my own and really took it in,” she said.
Raducanu burst onto the scene a year ago with a run to the Wimbledon fourth round, having come into the tournament ranked 338th in the world.
This time she arrived as the 10th seed and Grand Slam champion – and she was greeted as such by a passionate crowd that played its part in getting her through.
“I’m extremely pleased to have come through that match and looking forward to hopefully playing in front of you guys again,” she said in her on-court interview.
“I’ve been feeling it (crowd support) ever since I stepped on to the practice courts, people behind me going, ‘Emma, you’ve got this’. And I’m like, ‘Yeah, I’ve got this’.
“I’m just so happy to stay another day.”
She will face Caroline Garcia next after France’s former world number four edged British wildcard Lily Miyazaki 4-6 6-1 7-6 (10-4).
‘Switched-on’ Raducanu shakes off rust and injury
This was a difficult draw for Raducanu against world number 46 Van Uytvanck, who reached the fourth round here in 2018 after beating then-defending champion Garbine Muguruza in the second round.
The Belgian had also won two second-tier grass titles in the run-up to Wimbledon this year.
By contrast, the Briton’s grass-court campaign had been derailed by a left side injury that forced her to retire from her Nottingham opener in the first set and ruled her out of Birmingham and Eastbourne.
It meant she arrived at Wimbledon with just seven games on grass to her name this year, and she was playing only her seventh match as a professional on the surface.
“I definitely feel that because I didn’t play tennis for two weeks, then this week I’ve hit like an hour a day. My preparation wasn’t necessarily the greatest,” Raducanu told a news conference.
“But I know that when it comes to the matches, I feel like I really switch on. I don’t feel like I need a massive amount of preparation. Of course I do to build physically.
“I think a lot of it is mental and I definitely went out with the belief today. I know that I can compete with anyone on the other side of the court when I really go for it.”
Whether it was the occasion of walking through the new central entrance to Wimbledon’s main show court, or the lack of match practice, Raducanu made a slow start in her first service game as she fended off three break points in a lengthy game featuring six deuces.
After trading breaks midway through the first set, she made the key breakthrough with a break to love for 5-4, before a series of Van Uytvanck errors, including a backhand into the net on the second set point, handed the opener to the Briton.
Raducanu had the chance to take an early lead in the second set, but could not convert any of the six break points she had in the opening game.
She seemed to start moving a little slower between points in the second set, but a break for 5-4 quite literally put a spring in her step and she sealed victory with a beautiful crosscourt backhand after bringing Van Uytvanck to the net with a drop shot.
Centre Court leaped to its feet and Raducanu herself was jumping up and down as she celebrated the success.
Fresh from a ‘gap year’ that ‘went very well’
Raducanu was always going to get a rousing reception at her first Grand Slam on home turf since that magical US Open win last September.
She was the first qualifier to win the title and did so without dropping a set.
Centre Court had not had the chance to mark the achievement, but took its chance with huge cheers when she arrived and noisy excitement when she showed her class in a sometimes patchy encounter.
Raducanu added: “It feels incredible. From the moment the doors opened, I completely cherished every moment. I feel like everyone is so behind me.”
She arrived at her news conference wearing a T-shirt with Rafael Nadal’s ‘Raging Bull’ logo and said she is inspired by the Spanish 22-time Grand Slam champion, who has won the first two majors of this year.
“I think Rafa just embodies fight, that sort of energy,” said Raducanu.
She has already shown plenty of that herself and is still only in her first full year on the WTA tour.
“I’m 19, I just took a gap year and it went very well,” she added. “I’m waiting for Freshers’ Week in September. I’m still very new to it.”