West Yorkshire Police said a 37-year-old man was detained on Wednesday following the arrest of a 32-year-old woman. on Tuesday.
A spokesman said: “A second arrest has been made in connection to alleged threats made against MP Naz Shah.
“A 37-year-old man was arrested earlier today and remains in custody at this time.
“A 32-year-old woman who was arrested yesterday also remains in custody.
“Inquiries are continuing.”
Earlier this week Bradford West MP Ms Shah announced she was looking into the death of one of her constituents amid claims she may have been the victim of a so-called honour killing.
Samia Shahid, 28, from Bradford, died last week while visiting relatives in northern Punjab and West Yorkshire Police said it was working with the “relevant authorities” to establish the cause of death.
Ms Shah was suspended from the Labour Party in April over anti-Semitic posts on social media, but was readmitted in early July.