On 28 October 2016, the song entered the UK Singles Chart at #7. The following week, it went to #3. In its third week, it reached #1. In the United Kingdom, the song became their second #1, after "Rather Be" in 2014. The song also topped charts in Australia, Germany, Italy, Switzerland, Denmark, Austria, Belgium, Italy, Sweden, Finland, and New Zealand.
In the United States, "Rockabye" began at #100 on Billboard Hot 100 during the week of 24 December. It was Clean Bandit's first entry on the chart since "Rather Be" with Jess Glynne. The song reached number nine on the US Hot 100, becoming their second US top-ten hit after "Rather Be".