Harker was nominated by President Donald Trump to serve as an assistant secretary of the Navy (financial management and comptroller) and was confirmed on December 20, 2017[1] and sworn in on January 2, 2018.

[6] During his 20 years in the Coast Guard, Harker was responsible for financial reporting, setting policy, overseeing property management and preparing audits.

Harker's focus on mental health followed the Pentagon's August 2021 annual report to Congress, which cited an increase in suicide rates.

[8] To remove the stigma of seeking mental health counseling, Harker recorded a video in which he said he had sought mental health counseling three times in his life: his parents' divorce, his own divorce; recovery effort involving 80 men, women and children who died in a ferry disaster off the coast of Haiti.

In the video, Harker tells sailors, “In the course of your service, you may see and experience things most Americans won’t even think about ... don’t shelve those experiences away.”[9] To hire more psychiatrists and trained corpsman, Harker requested funds in the current Defense Department budget be reprogramed to invest in mental health to prevent sailor suicide.