Speaking ahead of the hearing in central London on Tuesday, Richard Page said he was being "punished" simply for believing it is in a child's best interests to be raised by a father and a mother.
Christian Legal Centre (CLC) lawyers representing him warned the case could have "significant consequences" for "anyone who expresses a Christian view in a public setting or even in a private social setting".
In February last year, an Employment Tribunal upheld a decision by Kent and Medway NHS and Social Care Partnership Trust (KMPT) in 2016 to remove him as a non-executive director.
The Trust unanimously decided it was "not in the interests of the health service" because Mr Page's actions were likely to have a "negative impact" in people's confidence in his role.
It took action after Mr Page discussed his views on adoption during a BBC News report. The coverage concerned was related to disciplinary action taken against him in his capacity as a magistrate.
Mr Page, who had served as a magistrate for 15 years, expressed his views on adoption during a closed-door consultation with two other magistrates about an adoption case in 2014.
He was subsequently disciplined after being reported to the Lord Chancellor and Lord Chief Justice.
Please pray for justice to be done in the case of Magistrate Richard Page in the Employment Appeal Tribunal today https://t.co/GGEUefLhOm— Andrea Williams (@A_Minichiello) January 22, 2019
Mr Page was told his views were discriminatory. He was banned from sitting as a magistrate until he underwent "equality training". In March 2016, Mr Page was removed from the magistracy.
Weeks later, Richard was suspended from his role at the KMPT. He was later denied the right to renew his four-year term when it became due for renewal.
Andrea Williams from the CLC commented: "The trust's decision to block Richard from returning to his role is an attack on the man and his views and nothing to do with the practical workings of the NHS.
"The freedom for Christians to hold and express their views is under threat."
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.