Commissioned December 7, 1943, at Quebec City, she arrived at Halifax on December 20 and commenced working up in St. Margaret's Bay, completing the process in Bermuda. She left Halifax at the end of February, 1944, to join EG C-1 and sailed for the U.K. with convoy SC.154, but was detached to Horta en route, escorting a tug and its tow, the rescue ship Dundee. Her next assignment was to escort the damaged HMCS Mulgrave, in tow from Horta for the Clyde. The three left the Azores on March 14 and joined convoy SL.151 (from Sierra Leone) three days later.
In May 1944 she was on the return leg of her second escort assignment. She was accompanied by two other Canadian frigates and two corvettes. The escort group has just handed off the convoy to another group of escorts, and were returning to the port of St. John?s Newfoundland.
Just before midnight on 6 May 1944, The ships were only 50 miles south of Cape Race, Newfoundland. Small icebergs scattered the area, confusing the radar picture. The ships sailed on, making good way to the safety of their favorite Newfoundland port. Little did they realize that U-548, a German submarine, lay in wait.
HMCS VALLEYFIELD, was traveling astern of the other ships. The Officer of the Watch had just called for the middle watch, when suddenly the ASDIC operator gave a sudden warning of the presence of a submarine. Just as Action Stations were called, a torpedo ripped into the port side of the VALLEYFIELD, causing a tremendous explosion. The ship was broken in two, and she quickly began to settle down into the water.
As the ship was sinking, most of the ship?s crew entered the ice-cold North Atlantic water, which when measured in the last watch, registered a temperature of a mere 32 degrees Fahrenheit. In addition, oily water choked the survivors, as they huddled together, helping each other to survive. Some clambered on top of wreckage, or clung to carley floats. Others remained in the water, buoyed by the life jackets.
Now that the ship had completely sunk, they found themselves alone, with their escorts virtually unaware of the deadly occurrence astern. Finally, HMCS GIFFARD, realizing that the VALLEYFIELD was missing, came to the scene to rescue survivors. However, as was the doctrine at the time, the rescue did not begin until she had spent valuable time searching for the u-boat which had caused the tragedy. By this time many men had given up, let go their hold on Carley floats or wreckage and sank from sight. A total of 125 men perished that night, all within the coastal shores of Newfoundland.
Torpedoed and sunk by U548 on 7 May 44, 50 miles south of Cape Race, Newfoundland. 125 of her ship's company lost.