The painter's father, Pierre, who appears to have died in about 1685, had a brother named André, or Andrew, who was active in London as a merchant trader in salt and wool, during the late 17th and early 18th centuries.

On 3 September 1696, Peter Monamy, aged 15, was bound as an apprentice for seven years by indenture to William Clark, a former (1687) Master of the Worshipful Company of Painter-Stainers, one of London's ancient guilds of craftsmen.

In Wine and Walnuts, William Henry Pyne mentions that Monamy served his apprenticeship on London Bridge, and that he exhibited his works in the window of his shop.

The next confirmed biographical item comes from the Westminster Poor Rate Book, which lists "Peter Monyman" as living in Fish Yard, off St Margaret's Lane, from 1723 to 1729.

From the above records, and subsequent comments, it can reasonably be surmised, as mentioned above, that Monamy set up in business on his own account, both as a decorator and easel painter, quite soon after being made free in 1704.

William Henry Pyne, an artist and raconteur (1769–1843) mentions that "Monamy, the marine painter, some of whose pictures were scarcely inferior to Vandevelde's, served his apprenticeship on London Bridge, and exhibited his works in the window of his shop, to the delight of the sons of Neptune, men and boys, who were seen in crowds gazing at his wondrous art.

His standing as a Liveryman of the Painter-Stainer's Company in 1726 was cemented by the donation to Painter's Hall of what was subsequently described by Thomas Pennant as "a fine piece of shipping", which is still in situ.

During the decade from 1730 to 1740 Monamy would have found that his practice became increasingly hard-pressed, as it met with the censure of groups of self-appointed arbiters of taste, and the importation of quantities of Old Master paintings from Italy and France, as well as of artists and aesthetic concepts from the continent.

In a review for the "Times Literary Supplement", 27 January 2012, of Coke and Borg's "Vauxhall Gardens", John Barrell points out that "a national art in the making was reinforced by a number of modern history paintings by Peter Monamy, of English naval victories".

In the period preceding Britain's crucial first bid for global naval supremacy, at Porto Bello in 1740, and during the mounting opposition to the appeasement policies and other political measures of Robert Walpole, England's long-serving Prime Minister, these sea-captains were among the most active and vociferous of his opponents.

It was reported in The Daily Post, a London newspaper, of Tuesday, 20 May 1740, that the Prince of Wales and Princess Augusta had selected "the Picture representing the taking of Porto Bello" for particular inspection during a visit to the Gardens the previous evening.

Monamy continued as the marine painter most esteemed by active serving seamen, even during his slow financial decline and loss of aristocratic patronage, and for many decades after his death.

In 1749 George Vertue expressed this reputation: "his industry and understanding in the forms and buildings of shipping with all the tackles ropes & sails &c which he thoroughly understood made his paintings of greater value; besides his neatness and clean pencilling of sky and water by many was much esteemed, especially sea-faring people, officers & others, merchants &c."[This quote needs a citation] Joseph Highmore noted, in 1766, that "A sailor … is a better judge of the principal circumstances which enter into the composition of a sea-piece, than the best painter in the world, who was never at sea."

[This quote needs a citation] Vertue goes on to relate that "he lived some years latter part of his life at Westminster near the river side, for the conveniency in some measure of viewing the water & sky; though he made many excursions towards the coasts and seaports of England to improve himself from nature [...] thus having run thro' his time [...] being decayed and infirm some years before his death, which happened at his house at Westminster the beginning of Feb 1748/9 [...] leaving many paintings begun and unfinished, his works being done for dealers at moderate prices [...] kept him but in indifferent circumstances to his end.

Well over a year after his death, on 26 July 1750, his studio possessions, pictures, prints, drawings, ship models, furniture and collection of china were auctioned, the sale lasting a full day.

In Mark Noble's Biographical History of England, 1806, under the entry for Monamy, it is stated that "Swaine, of Stretton Ground, Westminster, his disciple, and bred under him, was an excellent painter of moon-light pieces.

Since about that time, or a little earlier, there has been a flow of paintings entering the market, and now forming parts of otherwise reputable collections, which can only be described as pastiches, detectable as inauthentic when compared with works that have solid 18th century provenance.

"[3] A tendency of later critics and art historians is to suppose that Monamy experienced little competition as a marine painter, following the death of the Younger van de Velde in 1707.

As an indication of the esteem in which Monamy was held by a significant group of his fellow-Londoners, both as a person and as a practitioner of his craft, the following anonymous obituary, from The London Gazetteer of 9 February 1749, says: "Yesterday Evening was buried at St. Margaret's Westminster, Mr.Peter Monamy, greatly eminent for his Skill in Painting Sea Pieces; in which Art, as he was not equall'd by any of his Cotemporaries [sic], neither was he excell'd by many of the Ancients; but his Name and Character are too well known and establish'd among the Curious to need any artful Commendation to set them in greater Light to advance his Merit; neither can the warmest Praise add to his Fame when dead, who, in his Life, was the greatest Enemy to Adulation; and tho' some Notice is due to the Memory of so celebrated an Artist in Painting, yet his own Performances, which are extant in the World, will prove his most lasting Monument.