Merseyside Police have taken the 26-year old in after he was sent off for dissent during a match against Heart of Midlothian in December in which the Jambos saluted 2-1.
The Scottish Football Association have launched an investigation into the match after bookmakers reported irregular betting patterns and SFA chief executive Stewart Regan has confirmed Jennings' arrest.
"The Scottish FA has received notification from the Gambling Commission that the Motherwell FC player, Steve Jennings, was arrested at his home today by Merseyside Police," said Regan.
"While the investigation involves several other individuals outwith Scotland, it is important to stress that the evidence gathered throughout this thorough period of investigation has involved only one Scottish match.
"Motherwell FC are aware of the situation and will issue a response in due course. The Scottish FA will make no further comment at this stage."