The 20-year-old Santhosh won the light welterweight 64kg final 10-8 to clinch his maiden senior international gold medal. He last won a gold at the 2008 Youth Commonwealth Games in Pune.
Late last night, Jasveer Ahlawat (81kg) and Lakhbir Singh (69kg) lost their respective semifinal bouts to settle for bronze medals. The 18-year-old Gaurav Bidhuri was the other Indian bronze-medallist from the event after losing the light fly weight 49kg semifinals.
While Jasveer went down 8-12 to Australia's Commonwealth Games quarter-finalist Damien Hooper, Lakhbir was defeated 11-19 by Alexander Kunkov of Russia.
The duo's loss left Santhosh as the lone Indian finalist in the event, which is being held for the first time after the 2004 tsunami. And he did not disappoint by putting up a spirited performance.
"This is one of the best wins of my career, I am so happy, I don't have words to express," said the Andhra Pradesh boxer, who is also the reigning national champion.
"Alexander is of shorter height than me and I had closely seen the recordings of his previous bout. My plan was to hit and move and not allow him to build a tempo. I kept my guard low to invite him forward and mostly counter-attacked," he added.
Despite trailing 5-6 in the opening round, Santhosh kept his cool and the calculated approach paid off as he took a 7-6 lead.
In the third round, the Indian built on the lead to seal the issue in his favour.
The four medals this time is a marked improvement from India's performance in the previous edition, in which the country's boxers returned with just a couple of bronze medals.
Coach Jagdeep Hooda, who accompanied the team, said the boxers' performance is laudable considering they were up against top quality competitors.
"These guys hardly get a chance to compete in the international events because the top guys generally go. But they have proved their mettle against quality opposition here," he said.