She was born Emily Sarah Sellwood at Horncastle in Lincolnshire. Her father was a solicitor who would act for the Tennyson family many times over the years. Her mother, who died when Emily was three, was a member of the Franklin family, sister of Sir John Franklin, an explorer, and Sir Willingham Franklin. Emily first met Alfred Tennyson during childhood, but they did not become close until much later (when Alfred's brother, Charles, married Emily's younger sister, Louisa), and did not marry until 1850. For much of the intervening time, they did not see one another at all.
They had two sons, Hallam and Lionel. During Tennyson's lifetime, Emily was his strong supporter and employed her own talents in setting some of his lyrics to music. After his death in 1892, she devoted herself to helping her son write the authorised biography.