Anhelina Kalinina and Elizaveta Kulichkova were the defending champions, but both players chose not to compete in 2015.
Jeļena Ostapenko was the defending champion, but entered the Women's singles instead.
Tami Grende and Ye Qiuyu were the defending champions, but chose not to participate.
Luisa Veras Stefani is a Brazilian tennis player.
Līga Dekmeijere and Jelena Pandžić were the defending champions, having won the previous event in 2008. However, Dekmeijere has been inactive on the women's tour since 2015, while Pandžić retired from the professional circuit in 2017.
Hayley Carter is an American tennis player. She has a career high WTA doubles ranking of No. 36, which she achieved on August 31, 2020.
The 2018 Stockton Challenger was a professional tennis tournament played on outdoor hard courts. It was the third and fourth editions of the tournament and was part of the 2018 ATP Challenger Tour and the 2018 ITF Women's Circuit. It took place in Stockton, United States, on 1–7 October 2018.
Usue Maitane Arconada and Sofia Kenin were the defending champions, but chose not to participate this year.
Misaki Doi and Jil Teichmann were the defending champions, but Doi chose not to participate. Teichmann played alongside Madison Brengle, but they lost in the first round to Quinn Gleason and Luisa Stefani.
Asia Muhammad was the defending champion, but chose not to participate.
Hayley Carter and Ena Shibahara were the defending champions, but chose not to participate.
Ellen Perez and Arina Rodionova were the defending champions, but lost in the quarterfinals to Vania King and Claire Liu.
Choi Ji-hee and Han Na-lae were the defending champions, but lost in the quarterfinals to Laura Pigossi and Wang Yafan.
Olga Danilović and Tamara Zidanšek were the defending champions, but chose not to participate this year.
Katherine Sebov was the defending champion, but chose not to participate.
Quirine Lemoine was the defending champion, but chose not to participate.
Sharon Fichman and Maria Sanchez were the defending champions, but chose not to participate.
Quinn Gleason and Luisa Stefani were the defending champions, but Gleason chose to participate at the 2019 Henderson Tennis Open instead.
Maegan Manasse and Jessica Pegula were the defending champions, but chose not to participate.
Hayley Carter and Ena Shibahara were the defending champions, but Shibahara chose not to participate this year.
