This total, figures published by the Delaware Lottery show, was the lowest monthly amount since $4.1m was bet in July 2021.
Revenue for April reached $314,336, which was 64.5% lower than $895,299 in July last year and 43.2% down from $553,465 in March 2022.
Delaware Park retained top spot in the market, posting $151,674 in revenue from $2.1m in wagers.
Dover Downs placed second with $95,059 in revenue and a handle of $1.2m, while the Harrington Raceway followed in third, reporting $67,603 in revenue from $853,005 in wagers.
Players won a total of $3.8m from sports betting during the month, placing 142,465 bets in the process.