Her first volume, 'Lays of a Wild Harp,' appeared as early as 1835, when she was but seventeen. Encouraged by its favourable reception, she began to send verses without revealing her name to the 'Weekly Dispatch,' the 'Metropolitan Magazine,' and the 'New Monthly Magazine;' and Jerdan sang her praises in the 'Literary Gazette.' After a time she confined herself to the 'Weekly Dispatch,' where her first contribution had appeared under the signature 'C.' on 27 Nov 1836. In 1837 began to offer verse to the radical Weekly Dispatch, then edited by William Johnson Fox. She was a staple of its pages for the next ten years. She also offered material to The Literary Gazette, Metropolitan Magazine and New Monthly. 
Her work for the Dispatch and New Monthly was later pirated by George Julian Harney, the Chartist, for the Northern Star. Familiar with the London Chartist movement, in its various sects, she followed many of the older radicals in disagreeing with the O'Brienites and O'Connorites in their disregard for repeal of the Corn Laws. She also preferred the older Radicals' path of Friendly Societies and self-education.
In 1835, while only seventeen years of age she published her first volume titled Lays of a Wild Harp. In 1838, she published Melaia and other Poems, and from 1849 to 1854 wrote, edited, and published Eliza Cook's Journal, a weekly periodical she described as one of "utility and amusement." Cook also published Jottings from my Journal (1860), and New Echoes (1864); and in 1863 she was given a Civil List pension income of £100 a year.
Her poem The Old Armchair (1838) made hers a household name for a generation, both in England and in America. Cook was a proponent of political and sexual freedom for women, and believed in the ideology of self-improvement through education, something she called "levelling up." This made her a great favourite with the working-class public. Her works became a staple of anthologies throughout the century. She died in Wimbledon.