Marcia Furnilla came from a noble and distinguished family. She was from the gens Marcia who were of plebeian status, which claimed descent from Roman King Ancus Marcius. She was a daughter of Roman Senator Quintus Marcius Barea Sura and Antonia Furnilla. Her sister was Marcia, the mother of Ulpia Marciana and of future Roman Emperor Trajan. Her father was a friend to future Roman Emperor Vespasian (who was Titus' father) and her paternal uncle was the senator Quintus Marcius Barea Soranus, while her paternal cousin was the noble woman Marcia Servilia Sorana. Furnilla's paternal grandfather was Quintus Marcius Barea, who was Suffect consul in 26 and was twice Proconsul of the Africa Province, while her maternal grandfather could have been Aulus Antonius Rufus, a Suffect consul either in 44 or 45.

Marcia Furnilla was born and raised in Rome. She married Titus, widowed from his first marriage, in 63. The marriage between Titus and Furnilla was an arranged one.

This marriage for Titus was an influential one and promoted his political career. Suetonius describes Furnilla as a "very well-connected" woman. On September 17, 64, Furnilla bore Titus a daughter, Flavia Julia Titi or Julia Flavia in Rome.

Like Titus' first marriage, this one was short. Furnilla's family was connected to the opponents of Roman Emperor Nero and after the failure of the Pisonian conspiracy in 65, they were disfavored by the Emperor. Titus didn't want to be connected with any potential plotters and ended his marriage to Furnilla, but continued raising their daughter.

The fate of Furnilla afterwards is unknown. After her death, she was placed along with her mother in the mausoleum of Gaius Sulpicius Platorinus - a magistrate at the time of the first Roman Emperor Augustus - and his sister Sulpicia Platorina in Rome.