John Van Antwerp MacMurray's family correspondence includes correspondence with his parents Junius Wilson MacMurray and Henrietta Van Antwerp MacMurray, his sisters Edna and Ethel and their spouses, as well as his wife Lois, and his children Joan, Frank and Lois ("Bisi"). In addition, the subseries includes correspondence with his grandfather John H. Van Antwerp (1823-1903) and other members of the Van Antwerp family, as well as with his father-in-law Frank J. Goodnow and his wife, and other members of the Goodnow family. The files are alphabetically arranged, with maiden names used for the female members of the family, unless the correspondence started after they married. The majority of the series consists of the correspondence between John Van Antwerp MacMurray and his father Junius Wilson MacMurray, who died in 1898, and his mother Henrietta Van Antwerp MacMurray. The correspondence with both his parents documents MacMurray's life at boarding school in New Jersey (Captain Wilson's Collegiate Institute at Newton 1891-1895 and Lawrenceville School 1895-1898), which is supplemented by Junius Wilson's correspondence with the headmasters of both institutes (Subseries 2A).

The letters from John Van Antwerp MacMurray (a bachelor until he was 35) to his mother include extensive and often humorous descriptions of college life at Princeton University (1898-1902), his attempts to get a "footing" in the diplomatic service, and his subsequent diplomatic career. The correspondence is particularly rich for detail about his life and work at the American Legation at Bangkok, Thailand (1907-1908), the Embassy at St. Petersburg, Russia (1908-1911), and at the Peking Legation in China (1913-1917). The Peking correspondence includes interesting observations about the political situation in China and the position of Yuan Shikai. In China MacMurray started taking numerous photographs, many of which he sent to his mother (see series 8). MacMurray's postcards to his mother and sisters, which were printed from his negatives, often provide details that are not found with the photographs, and are therefore kept separately in a chronological arrangement (box 24-26). The correspondence for 1909-1914 includes entries that MacMurray copied from his diaries (see Series 4).

After 1916 MacMurray's letters to his mother include details about his family life, his time as counselor of the embassy in Tokyo (1917-1919) and as Minister to China (1925-1929), a position from which he resigned shortly after his mother's death in 1929. MacMurray's correspondence with his sisters Edna and Ethel complements his early letters to his mother, particularly his letters to Edna, with whom he could often be more frank. The later correspondence includes details about their respective family lives abroad (among other places, Edna MacMurray Robinson lived in Puerto Rico and the Philippines; Ethel MacMurray Wright lived in part in Indonesia).

Included in the series are MacMurray's letters to Lois Goodnow, whom he married in February 1916. A Bryn Mawr sophomore, Lois met MacMurray in Summer 1915 when she and her two cousins accompanied her father Frank J. Goodnow to China. Frank Goodnow was an advisor to the government of Yuan Shikai and had been MacMurray's professor at Columbia Law School. During their marriage the couple kept in close touch when work and family kept them separate. Of particular interest in this respect is the correspondence between April to November 1927, when Lois and the children were in the United States because it was not considered safe to stay in China.

Additional correspondence includes correspondence with the couple's children Joan, Frank, and Lois ("Bisi"), their life at boarding school and subsequent life. The correspondence with Frank Goodnow is not extensive, but includes correspondence about the offer to MacMurray to head the Walter Hines Page School of International Affairs at Johns Hopkins University, of which Goodnow was president until 1929.