Huntingdon said it is willing to pay $8 in cash or $6 in cash plus 0.16038492 of a Huntingdon share for each KEYreit unit.
However, unlike the Plazacorp offer, it did not put a limit on the amount of cash available.
The cash component of the offer from Plazacorp, which owns and develops real estate properties in Atlantic Canada, Quebec and Ontario, is subject to a maximum $59.5 million, representing 50 per cent of the price.
The remaining half is to be paid in Plazcorp shares.
"We are pleased to have created value for KEYreit unitholders through this process and believe that our amended and very attractive $8 per unit all-cash offer provides near term certainty for unitholders," Huntingdon president and chief executive Zachary George said in a statement.
Huntingdon already owns a 5.4 per cent stake in KEYreit.
The increase by Huntingdon was the second time the company has increased its bid for KEYreit. The company had originally made an offer of $7 per share, but later raised that to $7.50.
Huntingdon owns and manages a portfolio of 36 industrial, office, retail and aviation-related properties.
Units in KEYreit, which has 226 properties in nine provinces across Canada, were up four cents at $7.71 on the Toronto Stock Exchange.
Huntingdon shares closed up a penny at $12.35.