The bypolls are scheduled to be held to one Lok Sabha and two assembly seats.
"State party president Bashishtha Narain Singh has announced that we will not be taking part in the bypolls to the Araria Lok Sabha seat and Jahanabad and Bhabhua Assembly seats," a senior JD(U) leader said.
The bypoll in Araria was necessitated by the death of RJD MP Mohammad Taslimuddin. The BJP had finished second in the seat in the 2014 Lok Sabha polls, closely followed by the JD (U), which had contested the parliamentary polls separately.
The Jahanabad seat has fallen vacant after the death of RJD MLA Mundrika Yadav. The JD(U) had fought the 2015 Assembly polls in alliance with the RJD and the Congress.
The party is now an NDA constituent.
In Bhabhua, the bypoll has been necessitated following the demise of BJP MLA Anand Bhushan Pandey.
Meanwhile, RJD leader Tejashwi Yadav took potshots at JD (U) president Nitish Kumar, saying, "The decision not to contest any seat in the bypolls is indicative of the chief minister's capitulation before the BJP."