Monaghan suffered a second straight Division 1 defeat as they had two players sent off in Castlebar.
Monaghan led 0-4 to 0-2 early on but Stephen Gollogly's 29th-minute red card rocked the visitors as Mayo moved into a 0-9 to 0-6 advantage at the break.
Mayo made their player advantage count after the break as Aidan O'Shea's goal extended their lead to 1-13 to 0-8.
After Ryan Wylie's 55th-minute red card, Alan Freeman and Michael Sweeney added further Mayo goals.
Monaghan suffered a blow before the game when former All Star Conor McManus failed a late fitness test but they started well enough as an early free from goalkeeper Rory Beggan helped them take a 0-4 to 0-2 lead.
Mayo fought back to lead 0-7 to 0-5 before Gollogly responded with a Monaghan point but that was his final positive contribution to the afternoon as he then received his red card after an apparent off the ball tangle with Jason Doherty.
The home side pushed on to lead 0-9 to 0-6 at the break even though they had lost Seamus O'Shea to a black card.
His brother Aidan's 50th-minute goal ended the game as a contest as it extended Mayo's lead to 1-13 to 0-8.
Wylie's red card saw Monaghan's challenge completely imploding as Freeman and Sweeney helped themselves to late goals.
Allianz Football League results
Tyrone 0-11 1-08 Derry
Cavan 0-08 1-09 Down
London 0-06 1-18 Longford
Waterford 0-09 0-11 Carlow
Kerry 0-15 1-10 Dublin
Donegal 0-12 1-08 Cork
Mayo 3-15 0-11 Monaghan
Roscommon P-P Meath
Kildare 0-12 0-15 Westmeath
Galway P-P Laois
Limerick 1-06 2-16 Armagh
Louth 1-16 1-10 Wexford
Fermanagh 2-09 0-11 Tipperary
Clare 0-22 1-13 Sligo
Wicklow 2-06 2-18 Offaly
Leitrim 1-13 1-18 Antrim