Inclusion Criteria:  Adult participants with histologically confirmed diagnosis of adenocarcinoma of the breast with documentation of hormone receptor-positive status, irrespective of human epidermal growth factor 2 (HER2) status. NOTE: Participants with HER2-positive breast cancer are eligible only if they have completed their adjuvant anti-HER2 treatment and chemotherapy. With Stage IIB or Stage III, early invasive breast cancer at diagnosis who have undergone breast surgery for the current malignancy. Who have received prior aromatase inhibitors (AIs) (letrozole, anastrozole or exemestane or any sequence thereof) for at least 6 months and discontinued within 30 months from the initiation of the first AI administration due to AI treatment-related toxicity Absence of advanced/metastatic disease Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1 Capable of giving signed informed consent  Exclusion Criteria:  Medical history or ongoing gastrointestinal disorders potentially affecting the absorption of amcenestrant and/or tamoxifen. Participants unable to swallow normally and to take tablet and capsules. Predictable poor compliance to oral treatment. Active inflammatory bowel disease or chronic diarrhea, active hepatitis A/B/C, hepatic cirrhosis, short bowel syndrome, or any upper gastrointestinal surgery including gastric resection or banding procedures Prior breast cancer for which they received an AI Any other solid tumor or lymphoma diagnosis is not allowed except if the participant has been free from disease for ≥5 years Pregnant or nursing women, or women of child-bearing potential without a negative pregnancy test prior to randomization Participants with unrecovered acute toxic effects of prior AI therapy or surgical procedures Uncontrolled intercurrent illness, including psychiatric conditions that would limit compliance with study requirements Treatment with any another selective estrogen receptor degrader (SERD), tamoxifen or toremifene are not allowed as prior adjuvant therapy but could have been used as neoadjuvant therapy for a total duration of 3 months. Participants who were treated with a SERD, tamoxifen or toremifene in the neoadjuvant setting and who experienced disease progression are not allowed Participant is receiving concurrent HER2 directed therapy. Appropriate wash out between the last dose of HER2 directed therapy and randomization should be at least 4 weeks  The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.