The estate agent’s slump comes after reporting a profit of £3.8m in the same period last year.
Revenue declined by 9% as the sales business slumped, while planned investments in people, brand and technology also took their toll on the bottom line.
Mortgage revenue from Foxton’s Alexander Hall fell 3% to £4.1m from £4.2m year-on-year, with remortgages helping to underpin performance.
Foxton’s said its letting business has proved resilient, as revenue edged down 1% to £31.7m.
The estate agent’s balance sheet has no debt and a cash balance of £11.8m.
Chief executive Nic Budden said: “As expected the weak sales market impacted our performance in the first half of 2018.
“After a slow start to the year, performance in our lettings business improved throughout the period delivering another consistent result for the first six months.
“The property sales market in London is undergoing a sustained period of very low activity levels with longer and less visible transaction outcomes, which clearly impacts our business.
“We continue, however, to achieve market leading share of listings giving us confidence that our service led, results based model remains highly relevant to consumers.
“Going forward we will continue to invest in our proposition to enable us to maintain our differentiation in the minds of buyers, sellers, landlords and tenants.
“Looking ahead, availability of mortgage finance, absorption of stamp duty costs, and the return of confidence to the market will, amongst other factors, determine the timing and rate of increased activity levels.”
Foxton’s share price increased by 1.7% to 48.45p following the results, but this is a substantial drop from its height in February 2014 of nearly 400p.