Alaska Aces (2020–2022) Marcelino was drafted by the
Alaska Aces in the 2nd round (with the 5th pick) of the
2019 PBA draft. He was signed to a two-year deal. In his rookie season, he had little playing time as he only averaged 4.3 minutes and around two points per game. He then scored nine points in a win over the
TNT Tropang Giga.
Zamboanga Family's Brand / Master Sardines (2022–2024) 2022 season In 2022, he and his twin brother, Jayvee debuted in the
Maharlika Pilipinas Basketball League with the
Zamboanga Family's Brand Sardines. They started the season 5–0 with a win over the
Pasig Sta. Lucia Realtors in which he had 20 points, six rebounds, six assists, and five steals. In a win over the Sarangani Marlins, he had a near triple-double with nine points, nine rebounds, and seven assists to go along with his three steals. He then scored 21 of his 26 points in the fourth quarter and overtime to lead his team to a come-from-behind win over
Valenzuela XUR Homes Realty Inc. He got the MVP award in that year's MPBL All-Star Game, scoring 19 points, seven assists, and three rebounds as he led the South All-Stars to the win. For leading Zamboanga to an 18–3 record, Marcelino won the league MVP award and was also named to the Mythical Team. In Game 1 of their first round series against the
Muntinlupa Cagers, the Marcelino twins combined for 20 points, 10 rebounds, and 15 assists. Jaycee then delivered a triple-double in Game 2 with 24 points, 11 rebounds, 11 assists, plus six steals as they moved on to the division semis. In Game 1 of their semis against the Bacolod Bingo Plus, he led with a double-double of 21 points and 13 rebounds. They closed out the series in Game 2 in which he had 21 points, six rebounds, six assists, three steals, and one block. In the division finals, despite his 22 points and six rebounds, the
Batangas City Embassy Chill won the first game. Zamboanga then won the next game and in Game 3, he put up 14 points, 7 rebounds, 6 assists, and 5 steals to give Zamboanga the South Division title. In Game 1 of the National Finals, he was limited to just 12 points as the
Nueva Ecija Rice Vanguards got the win. In Game 2, despite his 26 points, seven rebounds, four assists, and two steals, Zamboanga lost by one point. His brother Jayvee then stepped up in Game 3 with 22 points, seven rebounds and three assists, although he was able to make an impact with nine points, 10 rebounds, nine assists, and four steals, as they extended the series. Nueva Ecija then beat them in Game 4 to claim the national championship.
2023 season In the preseason, Zamboanga won the
2023 MPBL Preseason Invitational. In a win over Valenzuela, Marcelino scored 22 points, six assists, four steals and four rebounds. He then recorded 17 points, eight assists, five rebounds, three steals and one block in a win over the
Pasay Voyagers. Against the
Marikina Shoemasters, he scored 22 points (with the last five of those points tying the game in the clutch), six rebounds, and three steals, but they lost due to a buzzer-beater from Marikina. In a win over the
Rizal Golden Coolers, he scored a career-high 27 points to go along with his five rebounds and four assists as they raised their record to 12–3. That season, he was an All-Star once again, contributing 16 points and eight rebounds as his team lost. In an overtime win over Pasig, he led with 21 points, four rebounds, two steals and two assists. Once again, Zamboanga got into the playoffs. In Game 1 of their first round series against the
Quezon Huskers, Marcelino almost put up a triple-double with 20 points, 10 rebounds, and seven assists to lead them to the win. They closed out that series in Game 3. In Game 1 of the division semifinals, he led with 18 points, eight rebounds, four assists and two steals, but also recorded six turnovers as they lost to the
Bacoor City Strikers. They lost the next game, and were eliminated from contending for the South Division title. Once again, he was named to the Mythical Team.
2024 Season In the opening game win against the
Valenzuela Classic, Marcelino tallied 26 points, eight rebounds, a steal, and 12 out of 21 from the field. In the same game, Marcelino achieved his 1,000th career points in his MPBL career in just 3 seasons, the 29th player to do so. In the next game, he recorded his new career-high with 31 points, along with four rebounds, three assists, and eight steals in a win over
Bicolandia Oragons. Marcelino scored 20 points, seven rebounds, six assists, and four steals in an 18-point comeback win over
South Cotabato Warriors. The next game, he scored 24 points, nine rebounds, three assists, and a block in an Overtime loss over the
Quezon Huskers. ==Career statistics==