Charles Robertson established himself early in his career as an Orientalist painter in the tradition of John Frederick Lewis and Frank Dillon. Increasingly, as he moved from oil to watercolour, he also became known for his atmospheric English landscapes, and especially ports and harbours. Charles Robertson was born in Liverpool, and probably studied art in London. However, by 1862, he had moved to Aix-en-Provence. From there he embarked on the first of a number of sketching tours, to Algeria, inspired by the idea of painting the Middle East. In 1863, while still living in Aix, he submitted an Algerian subject as his first exhibit at the Royal Academy of Arts.
On 12 December 1865, Robertson married Alice Mary Lonsdale in Cheltenham.
She was the eldest child of Captain William Lonsdale, who supervised the founding of Port Philip, Australia (which developed as Melbourne). Between 1867 and 1877, they would have six children, including Percy, who would also become an artist. By 1870, the family had settled at Bay Cottage, Common-Side, Walton on Thames, Surrey. A decade later, it had moved to Meadrow House, Meadrow, Godalming.
Robertson continued to make extended sketching tours, both in England and abroad, including those to Turkey and the Holy Land in 1872, and Egypt and Tangiers in 1876. His last trip was in 1889 to Egypt, Jerusalem, Damascus, Turkey, Italy and Spain.
Through the early 1880s, Robertson altered his practice, and focussed increasingly on watercolour. His mastery of the medium led to his election as an Associate of the Royal Society of Painters in Water-Colours in 1885 and a full member in 1891. He was also Vice President of the Royal Society of Painters and Etchers. He died in Walton-on-Thames later that year on 10 November 1891. A memorial exhibition of his work was held at the Fine Art Society in 1892.