The trucking and oilfield services company said it earned $44.2 million or 50 cents per share for the quarter ended March 31 compared with a profit of $58.8 million or 73 cents per share a year ago.
Revenue fell to $385.5 million from $426 million.
The company's oilfield services business earned $257.6 million in revenue, down from $296.6 million a year ago due to lower revenue from its Canadian Dewatering LP operations.
Mullen said it also saw lower demand for the parts of its business involved in the transportation of fluids and well servicing, along with reduced demand for rig relocation services.
The trucking and logistics business earned $129.1 million, down $1.5 million from a year ago.
Stephen Lockwood, Mullen Group's president and co-chief executive, said the company knew it would be difficult to top the first quarter of 2012, which was a record in terms of revenue and operating income.
"However, some extreme weather conditions in Western Canada, combined with bottlenecks in take-away capacity with some of our customers in the heavy oil plays of Alberta, were situations that we had little control over," Lockwood said in a statement.
"As well, we witnessed some competitive pressures in businesses tied to the servicing of wells as a result of decreased drilling and completion activity in Western Canada."
Mullen Group provides specialized transportation and related services to the oil and natural gas industry in Western Canada as well as trucking and logistics services.