As of 2023, there were 362 pupils enrolled at the school. There were 487 pupils at the school in 2006, 534 in 2005 and 369 pupils on roll in 2015. The school was established in 1894. One of its most famous ex-students was the poet and scholar
T. H. Parry-Williams, who first attended the school aged 11 in 1898. Previously, it was a grammar school and was called
Ysgol Ganolradd Porthmadog.
Rob Piercy, a successful local artist, was previously the art teacher at Ysgol Eifionydd. The school's head master is Dewi Rhys Bowen. In 2019, Ysgol Eifionydd will be celebrating 125 years of being a secondary school. ==Welsh language==