Born on May 22, 626 (9.9.13.4.1 6 Imix 19 Sotzʼ in the Long Count), he assumed the position of ajaw ("leader") of Piedras Negras on AD 639 (9.10.6.5.9 8 Muluk 2 Sip)—about two months after his father's demise and when he was only 12 years old.

The two scholars also note that Yaxchilan seems to have been in a bit of a Dark Age during Itzam Kʼan Ahk I's reign, lending more evidence to the idea that it was under Piedras Negras's control.

[7] However, despite all the bellicosity during his reign, Flora Clancy notes that his focus on taking care of his children "suggest[s] that [Itzam Kʼan Ahk I] also desired, and endeavored to achieve, peaceful conditions.

"[4] At the end of his life, Itzam Kʼan Ahk I's health began to fail him, and, recognizing that his demise was impending, he spent much of his remaining energy ensuring that his son, Kooj (meaning "Puma") was able to assume control of Piedras Negras.

[8] Itzam Kʼan Ahk I erected eight stelae, three panels, a throne, and a short stela-like column, making his tenure as ajaw "the most prolific in terms of royal patronage at Piedras Negras", according to Flora Clancy.

Carved on December 1, 642, this stela depicts the ajaw sitting on an elevated cushion; a "plain band" is wrapped around his chest, which Clancy argues represents his being "bound to office".

[1][10][12] O'Neil favors the former argument and writes that Itzam Kʼan Ahk I's mother was likely featured on the stela because she served for a time as her son's regent and was thus politically important.

[19][20][21] The ajaw on the panel is notably surrounded by subservient lords of nearby polities, implying that during Yat Ahk I's rule, Piedras Negras was the regional power.