The Brazil striker, on loan for six months at his first club from Manchester City, came on as a substitute 13 minutes after halftime and with five minutes to go backheeled Wesley's pass past goalkeeper Rogerio Ceni.
Robinho, looking to cement a place in Brazil's World Cup side, had already served notice his skills were undimmed despite a disappointing spell at City, when his shot at the end of a fine one-two with fellow striker Neymar was saved at full stretch by the keeper.
"I lacked a bit more physical condition and rapport with those kids who play so well but thank God I could score a wee goal," Robinho told reporters.
Teenager Neymar, seen as the new Robinho since his emergence at Santos, put them ahead with a penalty in the 38th minute after midfielder Arouca was brought down by Brazil defender Miranda.
The home side equalised nine minutes after Robinho had come on with substitute Roger's first touch, a header from a cross by Marcelinho, in the 'classico' in the Sao Paulo state championship.
GOOD KIDS
Santos coach Dorival Junior tempered the euphoria that has gripped fans since Robinho's return to the club he helped win the 2002 and 2004 Brazilian titles, starting him on the bench for his first match on home soil after five years in Europe.
Robinho, who cost City a British record 32.5 million pounds when he moved from Real Madrid in 2008, played as his team's main striker, not his usual position, scoring at the end of a quick counter-attack to put Santos top of the standings with 16 points from seven matches.
"It's a good start, to resume on the right foot was all I wanted. The team winning, me playing well and scoring was marvellous. Now I have to give continuity to the work," Robinho said.
"I know my potential but I was anxious to play, for things to turn out right. It was great.
"If we can improve our rapport and I can get fitter, we've got a lot to give Santos because these kids play very good football."
In the Carioca (Rio de Janeiro) championship, another of the many state tournaments that open the Brazilian season, lanky Uruguay striker Sebastian Abreu scored a hat-trick of headers as Botafogo beat Resende 5-2.
The victory puts Botafogo in the semi-finals of the first round of the championship with city's other big clubs, Flamengo, Fluminense and Vasco da Gama.
