He is the brother of Daniel Dillard.
His father died in 2008 after suffering from a heart attack. His mother remarried in 2011 and is now married to Ronnie Byrum.
Not much is known about Derick's childhood.
Before leaving for Nepal, Derick met Jim Bob Duggar, and the two became prayer partners. In March of 2013, he met Jim Bob's daughter, Jill Duggar, over the phone, and begin praying asking God for direction on whether he should continue getting to know Jill. The two began talking more seriously in August of 2013 at Jim Bob's suggestion. At the end of November, 2013, Jill and Jim Bob came to Kathmandu to meet Derick. During this trip, Derick and Jill entered an official courtship. This trip is featured on the 19 Kids and Counting episodes "Going the Distance for Love" and "The Big Question". After returning home the following January, as featured on the 19 Kids and Counting episode "A Toast to Love", Jill and Derick began to spend more time together in person.
In February of 2014, Derick asked Jim Bob's permission to propose to Jill. Derick had a song written by singer-songwriter Walker Hayes to have played before his proposal. The song "When He Made You" chronicles the couple's love story. On March 29, 2014, Derick proposed to Jill, and she answered "yes, totally!". This proposal is featured on the 19 Kids and Counting episode "The Proposal".
Derick married Jill Duggar on June 21, 2014, at Cross Church in Springdale, Arkansas. The couple shared their first kiss at the wedding in front of more than 1,000 guests. His best man was his brother, Daniel Dillard, and his groomsmen included two of Jill's brothers, John-David and Joseph. His ring bearers were Jill's brother, Jackson, and her nephew, Michael. After a honeymoon in Kill Devil Hills, North Carolina, the two settled into a home in Northwest Arkansas owned by Jill's father, Jim Bob.
Shortly after getting married, Jill and Derick discovered that they were pregnant with their first child, which they announced publicly on August 20, 2014. The couple announced their pregnancy to Jill's family on the 19 Kids and Counting episode "Jill's Secret". After nearly 70 hours of labor, Jill gave birth to a son, Israel David, via a C-section, on April 6, 2015. This birth is featured on the 19 Kids and Counting episode "Jill's Special Delivery".
Derick began attending Oklahoma State University, his parents' alma mater, in the fall of 2007. Derick's father, Rick, passed away in his sleep due to a heart condition on January 18, 2008, when Derick was 19 years old. In April of 2008, Derick tried out to play Pistol Pete, his school's mascot, a role that his father had once held, but did not make the cut. In April of 2009, Derick tried out again, and this time he got the part. Derick graduated from Oklahoma State University with a Bachelor's Degree in Business Administration, Accounting, and Economics 3.5 on 2011.
In February of 2014, Derick began working as a tax accountant at Wal-Mart's corporate headquarters in Bentonville, Arkansas. On June 10, 2015, Derrick announced he had left this job. Although it was originally speculated that Derick was quitting to move his wife and child away from northwest Arkansas after it was discovered that Jill had been molested by her older brother as a child, Derick later said that this decision had been planned for some time.
In January of 2012, Derick moved to Kathmandu, Nepal, to do volunteer work. While there, he led teams of American volunteers into villages in the Himalayan mountains to provide services and education to Tibetan refugees. He stayed there for two years, returning home in January of 2014.
In the summer of 2015, Derick and Jill announced that they would be leaving for a long-term mission trip. After a number of complaints from fans and donors alike that the couple was spending just as much time back in Arkansas as on the mission field, the couple began refunding donations to those who were unsatisfied. Much of their time in both locations has been featured on the show Counting On. Jill and Derick most recently returned to the US in May of 2017 in advance of their second child. On August 9, 2017, Jill and Derick announced that they were permanently relocating their mission to northwest Arkansas.
On October 2, 2016, Derick posted a photo on his Instagram account with a caption that said he was substitute teaching at Springdale High School. He has been photographed as a substitute teacher on other days too. It is unknown how often Derick works in this role.
Derrick is studied in the Cross Church School of Ministry. His ministry track was the international student ministry at the University of Arkansas through the C3 Ministry team at Cross Church. C3 is a ministry that caters to college students in the Fayetteville, Arkansas, area.
In March of 2018, Derick went on a mission trip to Mexico as a part of his ministry training. This trip included a few days of tourist activities, as well as street preaching and providing assistance to a local church in Guadalajara.
In April of 2018, Derick went on a mission trip to Colorado as part of his ministry training. This trip involved community outreach at a local church in Colorado Springs.
Derick is currently attending law school at the University of Arkansas.