To find the value of \( a \) when \( x = 1 \) is a solution to the equation \( (x + 2)^2 = a \), we can substitute \( x = 1 \) into the equation and solve for \( a \).
First, substitute \( x = 1 \):
\[ (1 + 2)^2 = a \]
Calculating the left side:
\[ (3)^2 = a \] \[ 9 = a \]
Thus, the value of \( a \) is \( \boxed{9} \).