The purpose of this study is to find out whether treatment with pasritamig and docetaxel prolongs radiographic progression free survival (rPFS) (the length of time from start of treatment until disease worsens as determined by scans or death due to any cause) when compared to treatment with docetaxel in participants with metastatic castrate-resistant prostate cancer (mCRPC; a cancer of prostate, a male reproductive gland found below the bladder, that grows despite low levels of male hormones).
Have histologically confirmed adenocarcinoma of the prostate
Have disease that is metastatic at the time of screening by computed tomography (CT) or magnetic resonance imaging (MRI) and 99m^Tc bone scan as determined by the investigator
Participants must receive ongoing androgen deprivation therapy (ADT) with a gonadotropin releasing hormone (GnRH) analog throughout the treatment or have had prior bilateral orchiectomy, and have serum testosterone less than or equal to (<=) 50 nanogram per deciliter (ng/dL) (<= 1.73 nanomoles per Liter [nmol/L]) at screening
Have progressed by PSA or CT/MRI or 99m^Tc bone scan on at least 1 novel androgen receptor pathway inhibition (ARPI) but no more than 2 different ARPI for any stage of disease. Must have discontinued ARPI before randomization into the study
Known history of either brain or leptomeningeal prostate cancer metastases
Participants with known breast cancer gene 1/2 (BRCA 1/2) mutations (germline or somatic) who have not received treatment with a poly (ADP-ribose) polymerase (PARP) inhibitor, unless not available or contraindicated
Prior or concurrent second malignancy (other than the disease under study)
Received cytotoxic chemotherapy for prostate cancer in any setting