Thrashed 100-54 on Monday, Gibraltar hit back and led Andorra 21 17 after the opening quarter and maintained that advantage at 38-34 at half-time.
The Andorrans, who have won this event in three of the past four years, outscored them 24-18 in the third quarter to take a two-point lead into the final 10 minutes.
Despite 18 points from Gibraltar's Adam Cassaglia, Andorra claimed victory by the slimmest of margins.
Andorra, who beat Malta 87-73 on Monday, are at the top of Group A alongside Moldova, who also had to come from behind before posting a 78-66 success against winless Malta.
Serghei Meresevschi poured in 27 points for Moldova, who trailed 32-24 after the opening quarter and 49-44 at half-time.
Etienne Bezzina had 14 points for Malta.
In other Promotion Cup action, Azerbaijan made it two wins from two in the European Promotion Cup for Men after downing San Marino 86-74 on Tuesday.
Fresh from their 82-62 victory over Wales on Monday, Azerbaijan were quickly out of the blocks against San Marino and were 32-15 ahead after the first quarter.
San Marino, who also lost their opening match 84-76 to Albania, refused to give up though and won the next quarter 27-17 before trimming another point off Azerbaijan's lead in the third quarter.
That left San Marino trailing by six heading into the final quarter, but Azerbaijan had too much left in the tank and eased away late on to take the spoils.
Forward Tahir Bakhshiyev paced the victors with 21 points while Flavio Bottiroli was the star for San Marino, scoring a game-high 28 points and hauling down seven rebounds.
In Tuesday's other game in Group B, Albania also picked up their second win of the competition with a 91-73 triumph over Wales.
Albania dominated from start to finish and won all four quarters against their struggling opponents. Gerti Shima was Albania's leading light with 23 points, eight rebounds and three steals.
However, the best individual performance came from Wales' Stuart Paul Robbins, who poured in a game-high 36 points and hauled down 11 rebounds.