Pengolodh was born in Nevrast to a Ñoldorin lord and a Sindarin lady. Early tales about the Fall of Gondolin mention him as one of the lords of the city, and ruler of the Twin Folk of the Pillar and the Tower of Snow. As one of the Lambengolmor, he was known as the Sage of the Ñoldor, and counted as the greatest Loremaster since Fëanor and Rúmil. He was also the tallest of the Elves of Gondolin.
Pengolodh escaped the sack of the city with Tuor and Idril's company of survivors, and followed them to the Mouths of Sirion. He is not further mentioned in writing, but since the Annals of Beleriand are attributed to him, as well as the edited Annals of Aman (furthering the work of Rúmil), he must have stayed in Lindon for at least a while after the War of Wrath, so that the Dúnedain could copy his work.
It was during his stay at the Mouths of Sirion that Pengolodh did the majority of his work. Basing on information obtained from the refugees of Doriath, he made copies and extracts of documents written in Cirth, possibly preserving them as an active writing system.
Later, in the Second Age, he lived in the Ñoldorin kingdom of Gil-galad in Lindon. Pengolodh was one of the few Elves admitted into Khazad-dûm, where he might have learned Khuzdul. Pengolodh left Middle-earth during the War of the Elves and Sauron and after the fall of Eregion, and left for Tol Eressëa, last of the Loremasters to leave Middle-earth. After removing himself to Tol Eressëa, Pengolodh dwelt in a village called Tavrobel (or Tathrobel). Centuries later, Ælfwine spoke with him there.
Pengolodh's only appearance was in the The History of Middle-earth, where he is said to be the author of many works, including the Annals of Beleriand, a work which was developed by Tolkien at the same time as The Silmarillion, and from which Christopher Tolkien drew much information to establish the published Silmarillion. Various late essays by Tolkien dealing with linguism are presented as being the work of Pengolodh, including the essay Quendi and Eldar.
Early Tolkien texts stated that, after Pengolodh moving to Tol Eressëa, the figure of Gilfanon, which fulfilled a similar role as a chronicler of the annals of Beleriand in earlier works, likely became this character as well in Tolkien's mind.
The many spellings of his name are Pengolod, Pengoloð, Pengoloth, and Pengoloþ—the ending in all cases representing the Voiced dental fricative. The name Pengolodh was a Sindarized form of his Quenya name Quendingoldo.