Medley entered the Royal Navy in 1703, and in 1706 was midshipman of the 80-gun HMS Somerset with Captain Price at the relief of Barcelona.

In 1722, while commanding the 50-gun HMS Leopard in the Mediterranean, he seized a ship named the Revolution, lying within the mole of Genoa, on information of her being in the service of the Old Pretender.

On 19 June 1744 he was promoted to be rear-admiral of the white, and in the following winter commanded a squadron cruising in the Channel Soundings for the protection of trade.

The service was one of blockade and co-operation with the allied armies in the War of the Austrian Succession, who in the winter of 1746–7 invaded Provence; but, after an unsuccessful attack on Antibes, they were obliged to retreat.

[1] George Rodney served with him on two ships at the beginning of his career with Medley acting as a mentor to the younger man.