At the time of Marjorie's birth, her father Robert was Earl of Carrick. Marjorie was named in honour of her father's mother, Marjorie, Countess of Carrick and his maternal grandmother. Her mother Isabella of Mar was the daughter of Domhnall I, Earl of Mar and Ellen of Wales (1246-1295), who was the illegitimate daughter of Llywelyn the Great Prince of Gwynedd. Isabella died at the age of nineteen, soon after giving birth to her daughter and was buried at Paisley Abbey in Renfrewshire.
Marjorie's parents were said to have been very much in love, Robert the Bruce did not remarry until Marjorie was six years old. In 1302, Robert took as his second wife, the thirteen year old Elizabeth de Burgh, daughter of Richard Óg de Burgh, 2nd Earl of Ulster, (one of Edward's most prominent Anglo-Irish supporters) and Margarite de Burgh, Elizabeth became the young Marjorie's stepmother. On 27 March 1306, Robert the Bruce was crowned King of Scots at Scone, and Marjorie, then aged nine, became a Princess of Scotland.
Three months later, in June, 1306, her father was defeated in battle by the forces of King Edward I of England at Methven. Robert the Bruce sent his daughter, Marjorie, his wife Elizabeth and his two sisters north to Isabella MacDuff, Countess of Buchan for their safety, they were escorted by King Robert's brother, Niall Bruce and the Earl of Atholl. It was intended that they would then take refuge in Orkney, but were besieged by the English at Kildrummy Castle, after the castle was taken, the English had Niall Bruce hung, drawn and quartered, along with all the male defenders of the castle, but the royal ladies, escorted by the Earl of Athol, escaped on to Tain, to the north of Inverness, where they were desperately hoping to obtain a boat. They were captured by the Earl of Ross, a supporter of the Comyns, in the sanctuary of St. Duthac and sent to Edward of England, then at Lanercost Priory in Cumberland.
Edward then sent his hostages to different places in England. Marjorie went to the Gilbertine convent at Watton, her aunt Christina Bruce was sent to another convent, Queen Elizabeth de Burgh, who was treated more leniently since Edward wished to ensure the loyalty of her father, Richard de Burgh, was placed under house arrest at a manor house in Yorkshire and Marjorie's aunt Mary Bruce and the Countess of Buchan, who had crowned Robert the Bruce, were imprisoned in wood and iron lattice cages, exposed to public view, Mary's cage at Roxburgh Castle and Countess Isabella's at Berwick Castle. The Earl of Atholl was hanged and his head displayed on London Bridge. Even Edward's ardent admirer, Sir Maurice Powicke wrote of his 'peculiar ferocity' in the instance of these women prisoners.
The Countess of Buchan remained in her cage for nearly four years, a spectacle for the curious, she was treated like an animal in a menagerie, until in 1310, when Edward II allowed her to be taken to the House of the Carmelites at Berwick. For the next four years, Marjorie herself endured solitary confinement, a cage was built for her at the Tower of London, but Edward reconsidered and instead sent her to the convent. Christopher Seton, Christina Bruce's husband, was executed.
King Edward I breathed his last at Burgh on Sands on 7 July 1307 and was succeeded on the English throne by his ineffectual son, Edward II, who continued to hold Marjorie a prisoner in a convent for around seven more years. She was finally released in around 1314, possibly in exchange for English nobles captured after the Scottish victory of the The Battle of Bannockburn. Marjorie was escorted back to Scotland under the escort of Walter Stewart, a descendant of the Walter FitzAlan who founded Paisley Abbey.
The young Walter Stewart, 6th High Steward of Scotland had distinguished himself at the Battle of Bannockburn and was rewarded by the king with the hand of Marjorie Bruce. Her dowry included the Barony of Bathgate in West Lothian.
Two years after her marriage, on 2 March 1316, a heavily pregnant Marjorie was riding in Gallowhill, Paisley, Renfrewshire when her horse was suddenly startled and threw her to the ground at a place called 'The Knock.' Marjorie was seriously injured, her fall caused a dislocation of her neck bone. She went into premature labour and was delivered of a son by ceasarian section at Paisley Abbey, surviving the birth by a few hours at most. She was nineteen at the time of her death, in common with her mother, who was also nineteen years old when she died in childbirth. At the junction of Renfrew Road and Dundonald Road in Paisley, a cairn marks the spot near to where Marjorie reputedly fell from her horse. She was buried at Paisley Abbey.
Her only son Robert eventually succeeded his childless uncle David II of Scotland in 1371 as Robert II, King of Scots. Marjorie's descendants include the House of Stuart and all their successors on the throne of Scotland, England and the United Kingdom