Merriweather spent much of his time between New York and London, and as from 2009 resided in East Harlem. Since the age of 18, Merriweather has had a tattoo on his inside-right forearm bearing the Latin phrase for "love or money". Merriweather indicated in 2009 that he planned another tattoo for his back – a 100-word excerpt from the last verse of the poem "Jim Jones", quoted in Robert Hughes' book The Fatal Shore, which includes "For night and day ... we toil and toil".
Merriweather's debut solo album, Love & War, also produced by Ronson, was released in June 2009, which reached number two on the UK Albums Chart and peaked in the top 10 on the Swiss Albums Chart. It was preceded by the singles "Change" (February) and "Red" (May), which both made the top 10 on the UK Singles Chart. "Change" appeared in the top 10 on the Swiss Singles Top 75. While "Red" was a top 10 hit on the Danish and Irish Singles Charts. On the ARIA Albums Chart, Love & War reached the top 40 and "Change" peaked in the top 50 on the related singles chart. At the ARIA Music Awards of 2009, he won the Best Male Artist category for Love & War.
At the 2009 O2 Wireless Festival in Hyde Park London, Merriweather headlined the second stage where Ronson supported him for half a set on guitar. Merriweather has appeared on television programmes such as The Justin Lee Collins Show and Britain's Got More Talent. He performed his single "Red" on T4 On The Beach 2009 in Weston-super-Mare.
Merriweather appeared as the musical guest on Late Night with Jimmy Fallon on 14 July 2009, performing "Change", and Letterman on 18 February 2010 when he performed "Red".