He was the son of Hugh McMechan and Lizzie Jane McMechan. In 1901 the family are living in house 4, Ballybranagh Lower, Ardglass, Co. Down. By 1911, the property is known as house 2, Ballybranagh, Ardglass, Co. Down. James is not recorded here.
McMechan would have joined the Belfast Banking Company around 1909 and worked in Pettigo, Cookstown and Downpatrick branches.
On 28th September 1912, McMechan and members of his family, Hugh and James signed the Ulster Covenant at the Balee Meeting House, Ardglass or at Castlewellan.
McMechan served with the 10th Bn. Royal Inniskilling Fusiliers and attained the rank of Captain. He was awarded the Military Cross (MC).
The London Gazette dated 17th September 1917 records his citation as
“For conspicuous gallantry and devotion to duty in leading his company during an attack. He personally showed them how close they could keep to the barrage, and with great courage and skill he outflanked and wiped out an enemy machine gun and its crew without a single casualty to his own men. His coolness and fine leadership contributed very largely to the success of the operation.”
The Belfast Banking Company 'Roll of Honour' booklet records McMechan as having been 'previously wounded' with his last known address as 'prisoner of war'.
The National Archives records a Medal Index Card as follows:
Royal Inniskilling Fusiliers, Captain
Following his demobilisation after the Great War, McMechan returned to work.
McMechan died on 23rd November 1933.