Just as in his opener against Francisco Cerundolo, Nadal dropped the third set of this match, but he regrouped, as he had two days earlier, to finish it in four.
A 6-4 6-4 4-6 6-3 victory for the 36-year-old will do the job for round two, but it was laboured at times on Centre Court from Nadal, a day after title favourite Novak Djokovic delivered a masterclass against Thanasi Kokkinakis.
Australian Open and French Open champion Nadal sealed it with an ace, his 16th consecutive win in a grand slam match, and the lack of polish at this early stage can be forgiven, given his lack of preparation on grass as he underwent treatment on his troublesome foot.
World number 106 Berankis forced breaks to lead early in the second and third sets, and although the Lithuanian was pegged back quickly enough by Nadal on the first occasion, he held his nerve to take the third set.
A rain delay came when Nadal was 3-0 clear in the fourth set, and that was only an inconvenience, Nadal wasting little time in finishing the job.
With Matteo Berrettini and Roberto Bautista Agut both pulling out of Nadal's half of the draw due to COVID-19, and Denis Shapovalov losing on Thursday to Brandon Nakashima after reaching the semi-finals last year, it is hard to see who might deny the Spanish two-time champion a place in the final, unless Nick Kyrgios or Stefanos Tsitsipas fancy the task. Italian Lorenzo Sonego will be the next to try.
Nadal said: "Every day is a challenge. That's the truth. I didn't play much on grass in the last three years. I need to improve, but I think the fourth set was much better. I think it was a good level of tennis in that set and the serve worked much better at the end of the match and I was able to play more aggressive, while at the beginning there were too many mistakes.
"It's important for me to accept things are not perfect and just keep working, be humble and accept the challenge.