The world number one produced a best throw of 88.55 metres on his final attempt to secure the continental title. India’s Yashvir Singh took silver with a personal best of 85.72m, while compatriot Rohit Yadav claimed bronze with 84.35m.
Pakistan’s Olympic champion Arshad Nadeem finished fourth with 80.29m.
Pathirage, 23, had a difficult start with a first-round throw of just 73.53m — the only mark below 80 metres he has recorded this season. He recovered strongly, launching 88.33m in the fourth round to take the lead before improving to 88.55m with his last effort.
The victory completes a remarkable year for the Sri Lankan. He entered the Asian Games having won all but one of the competitions he contested, including gold at the Commonwealth Games, the Diamond League final and the Ultimate Championships in Budapest.
Earlier this season Pathirage threw a national record and world-leading 92.62m at the Rome Diamond League, becoming only the fourth man in history to surpass 92 metres in a single year.
In the women’s javelin, China’s Yan Ziyi dominated with a Games record of 70.46m on her first throw. Japan’s Olympic champion Haruka Kitaguchi took silver with 62.70m, while compatriot Sae Takemoto earned bronze with a season’s best of 62.15m.
Pathirage’s gold adds further lustre to an already exceptional campaign and underlines Sri Lanka’s growing strength in the event.