Neffa made his international debut for the Paraguay national football team on 1 July 1989 in the 1989 Copa América match against Peru (5–2) win, in which he scored once (2–1).
Paraguayan player Neffa first appeared internationally for the Paraguay national football team on 1 July 1989 during the 1989 Copa América tournament against Peru. He contributed to his team's success with one goal (2–1) in their 5–2 win.