The agency beat DDB London and Maher Bird Associates (MBA) in a three-way pitch, handled by Creativebrief.
St Luke's was the incumbent on the account and had worked with RNIB for eight years, but did not repitch for the business. The agency won the business from JWT.
Arthur London will be responsible for refining RNIB's strategy over the next five years as it seeks to build a new brand message and also target beneficiaries, which significantly contribute to the charity.
Last month, RNIB launched a 90-second TV ad that asks viewers to donate £3 a month to enable the charity to support blind and partially sighted people.
Voiced by 'Downton Abbey' actor Jim Carter, the ad was inspired by a letter from a 12-year-old girl who had lost her sight, but continued to attend school. The letter thanked the RNIB for its national Talking Book Service, which allowed her to read with her friends.