If a Catholic were to walk into Trinity Evangelical Lutheran Church in New Haven, Conn., he or she would not feel out of place. The altar is centrally located, vested in green for Ordinary Time and flanked by a lectern and pulpit. An altar rail separates the sanctuary from the nave. Daylight streams in from stained-glass windows depicting the Virgin Mary and the Christ child.

A Catholic would also feel comfortable at a typical Lutheran Sunday liturgy. A procession is followed by introductory and penitential rites, the Scripture readings are the same as those read in Catholic Mass on most Sundays and bread and wine are blessed and shared during Communion.

A Catholic would also feel comfortable at a typical Lutheran Sunday liturgy.

Of course, there are differences. For example, Trinity Lutheran does not have Stations of the Cross hanging on the wall, and the congregation’s response is “and also with you,” rather than “and with your spirit.”

Yet the common elements of both traditions is an important theme of this year’s historic commemorations. On Oct. 31, Christians around the world will be marking the 500th anniversary of the Reformation. Martin Luther is traditionally believed to have nailed his 95 Theses to All Saints’ Church in Wittenberg, Germany, on Oct. 31, 1517, thus catalyzing Protestant reformations across Europe. This anniversary also celebrates more than 50 years of official dialogue between the Lutheran and Roman Catholic churches following the Second Vatican Council.

“I think now more than ever, we are coming to realize that there is so much more that unites us than divides us,” says Rev. Ryan Mills, Pastor of Trinity Lutheran, about the 500th anniversary. At the Bible study before service, Pastor Mills and about 10 parishioners discuss the upcoming commemoration while studying Luther’s sermons on Easter readings. They express gratitude for more open communication with their Catholic counterparts.

It may be surprising for Catholics to recognize shared elements of faith with Lutherans. Similarly, a “large part of what it means to be Lutheran is to have that Catholic identity,” says Jonathan Sanchez, a third-year master of divinity student at Yale Divinity school. Mr. Sanchez, who regularly attends Trinity Evangelical while at school, wants Lutherans to remember that they are grounded in the Catholic traditions that shaped Luther. “What the Lutherans maintained in the 16th century,” Mr. Sanchez argues, “is just as important as what they reformed.”

Similarly, a “large part of what it means to be Lutheran is to have that Catholic identity.”

Though today’s Lutherans and Catholics may feel more unified, obstacles remain to sacramental unity between the churches. The 1999 Joint Declaration on the Doctrine of Justification allowed Lutherans and Catholics to express a common understanding of “justification by God’s grace through faith in Christ.” The central issues for which Lutherans and Catholics mutually condemned each other in the 16th century are no longer church-dividing. The issues of church and ministry—particularly the ordination of women, married clergy and apostolic succession—are today’s main challenges.

Looking forward to the anniversary, Trinity Lutheran parishioners are praying for full communion between Catholics and Lutherans. They do not celebrate division in the Body of Christ. The Evangelical Lutheran Church in America (E.L.C.A.), the largest Lutheran denomination in the United States, believes in the true presence of Jesus Christ in Holy Communion. E.L.C.A. churches like Trinity Lutheran invite all baptized Christians to receive Communion at their churches on Sundays.

For Lutherans interested in ecumenical relations, not being welcome to share in Catholic sacraments can be painful. “It’s not fair,” one parishioner told America, “because any Christian can receive the sacraments here.”

Karen Johnson and Robert Quinlan know this pain intimately. Originally hometown friends, Ms. Johnson and Mr. Quinlan reconnected after their first spouses passed away. Today, Ms. Johnson, a parishioner at Trinity Lutheran, is preparing to marry Mr. Quinlan, a Roman Catholic. They developed a rhythm of attending Catholic Mass on Saturday evenings and service at Trinity Lutheran on Sundays.

As evident at Trinity Lutheran, there exist ways to celebrate Lutheran identity while also recognizing partnership and prayer with Catholic counterparts.

But Ms. Johnson knows the pain of Catholic-Lutheran tensions. When she was growing up, her Catholic cousins told her younger brothers that they were going to hell because they were not Catholic. Later in life, a priest publicly told her she was not welcome when she went up for Communion at her Catholic granddaughter’s Confirmation. Today, she is grateful for Pope Francis, whom she sees as moving away from the pain of the past.

As they prepare for marriage, Ms. Johnson and Mr. Quinlan join others who are excited about celebrating the dialogue between the churches. Mr. Quinlan did not start learning about Lutheranism until he reconnected with Ms. Johnson. He says it is important for Catholics to learn about Lutheranism in order to recognize what they hold in common and grow more deeply in their faith.

They both, along with others at Trinity Lutheran, demonstrate the importance of relationships in ecumenical dialogue. Through encountering the other as a friend and partner, long-held divisions are bridged.

The 500th anniversary can be an opportunity for what Mr. Sanchez and others call “Lutheran triumphalism.” But narratives that over-emphasize Lutheran developments over the existing Catholic tradition perpetuate real division in the church. As evident at Trinity Lutheran, there exist ways to celebrate Lutheran identity while also recognizing partnership and prayer with Catholic counterparts.

With Pope Francis and Catholic leaders making institutional efforts to promote unity among Christians, the work of ecumenism should also flourish at the ground level. Pastor Mills and his parishioners can offer Catholic parishes a model of friendship and prayer while both Catholics and Lutherans await full sacramental unity.

Angelo Jesus Canta is a graduate student of theology at the Boston College School of Theology and Ministry and former O’Hare Fellow at America. He studied Marian devotion in Italy and China as a Ricci Scholar at Loyola University Chicago.