There currently is one option to travel by night train from Basel to Duisburg, taking between approximately 5 and 6 hours: Namely the ICE 100 operated by DB.
Deutsche Bahn (DB) exited the actual night train business in 2016. However, it operates around a dozen Intercity and Eurocity trains that run exclusively at night. These trains only have first and second class seats. The cars remain lit throughout the night and the seats cannot be reclined.
For the next 7 dates with connections, the cheapest offer starts at 70 EUR. Check our connection pages below for all availabilities!