Both incidents occurred in the first quarter of the Browns' 33-30 overtime victory.
The first came less than two minutes into the contest when Ngata punched Cleveland rookie left offensive tackle Joe Thomas following a Baltimore fumble recovery.
Browns wide receiver Braylon Edwards fumbled after a 6-yard catch and the ball was recovered by Ravens middle linebacker Ray Lewis, who was tackled by Thomas at the Baltimore 45-yard line. But Ngata felt Thomas intentionally went for Lewis' knees and slugged the rookie tackle.
Ngata was penalized 15 yards for a personal foul and acknowledged after the game that he expected to be fined.
The sanction against Lewis was for unsportsmanlike conduct, for which he was penalized 15 yards later in the first quarter.
Lewis caught a 25-yard pass and, after being tackled, spiked the ball in front of the Ravens' bench. Lewis, of course, spent the first seven seasons of his eight-year career in Baltimore. He was released this spring and signed with the Browns.
It is not known if either player will appeal the fines.
In other incidents from last weekend's games, Tennessee Titans offensive lineman Daniel Loper and Chicago Bears linebacker Rod Wilson were each fined $5,000 for unnecessary roughness fouls in their teams' respective games.
Len Pasquarelli is a senior NFL writer for ESPN.com.