Although not definitive, Laërtius must have lived after Sextus Empiricus (c. 200), whom he mentions, and before Stephanus of Byzantium and Sopater of Apamea (c. 500), who quote him. His work makes no mention of Neoplatonism, even though it is addressed to a woman who was "an enthusiastic Platonist". Hence he is assumed to have flourished in the first half of the 3rd century, during the reign of Alexander Severus (222–235) and his successors.
The precise form of his name is uncertain. The ancient manuscripts invariably refer to a "Laertius Diogenes", and this form of the name is repeated by Sopater and the Suda. The modern form "Diogenes Laertius" is much rarer, used by Stephanus of Byzantium, and in a lemma to the Greek Anthology. He is also referred to as "Laertes" or simply "Diogenes".
The origin of the name "Laertius" is also uncertain. Stephanus of Byzantium refers to him as "Διογένης ὁ Λαερτιεύς" (Diogenes ho Laertieus), implying that he was the native of some town, perhaps the Laerte in Caria (or another Laerte in Cilicia). Another suggestion is that one of his ancestors had for a patron a member of the Roman family of the
Laërtii. The prevailing modern theory is that "Laertius" is a nickname (derived from the Homeric epithet Diogenes Laertiade, used in addressing Odysseus) used to distinguish him from the many other people called Diogenes in the ancient world.
His home town is unknown (at best uncertain, even according to a hypothesis that Laertius refers to his origin). A disputed passage in his writings has been used to suggest that it was Nicaea in Bithynia.