Not technically. Maryland, though geographically very much in the middle, was considered a Chesapeake/Southern Colony, in contrast to the middle colonies like Pennsylvania, New York, New Jersey, and Delaware.
Because it is borderline, it is important to look at the society and practices of the colony to better understand it. Maryland was heavily involved in agriculture and, in particular, tobacco farming—much like the other Southern Colonies. The heavier the reliance on this type of business, the more a Colony related to the South, by nature of their economies. Additionally, Maryland was a heavy slave state/colony, while the northern "Middle Colonies" began industrializing much earlier and they relied much less on slave labor for their production, separating Maryland further from the Middle Colonies.
The Middle Colonies are New York, New Jersey, Pennsylvania, and Delaware. Maryland is considered a Chesapeake or Southern Colony. Historically, it has more in common with Virginia than it does New York or Pennsylvania.
The Middle Colonies are known for their successful agriculture and religious tolerance. The Middle Colonies also were not very dependent on slavery. Maryland had many slaves in order to work the large tobacco farms. Maryland remained a slave state until the Civil War.
Maryland's close ties to the South would continue well after the colonial period. During the Civil War, it was only through occupation that Lincoln was able to keep Maryland within the Union. Also, the mayor of Baltimore was arrested for speaking out against the war. While Maryland never really joined the Confederacy, many of her native sons died for the Confederate States.