diff --git a/src/Unitful.jl b/src/Unitful.jl
index 359fee5d..9eb3339d 100644
--- a/src/Unitful.jl
+++ b/src/Unitful.jl
@@ -786,10 +786,11 @@ isless(x::Number, y::Quantity) = _isless(promote(x,y)...)
     .<=(x::Number, y::Quantity) = x <= y
 end
 
-isapprox{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}) = isapprox(x.val, y.val)
-isapprox(x::Quantity, y::Quantity) = isapprox(uconvert(unit(y), x).val, y.val)
-isapprox(x::Quantity, y::Number) = isapprox(uconvert(NoUnits, x), y)
-isapprox(x::Number, y::Quantity) = isapprox(y,x)
+isapprox{T,D,U}(x::Quantity{T,D,U}, y::Quantity{T,D,U}; atol=zero(Quantity{real(T),D,U}), kwargs...) =
+    isapprox(x.val, y.val; atol=atol.val, kwargs...)
+isapprox(x::Quantity, y::Quantity; kwargs...) = isapprox(uconvert(unit(y), x).val, y.val; kwargs...)
+isapprox(x::Quantity, y::Number; kwargs...) = isapprox(uconvert(NoUnits, x), y; kwargs...)
+isapprox(x::Number, y::Quantity; kwargs...) = isapprox(y,x; kwargs...)
 
 function isapprox{T1,D,U1,T2,U2}(x::AbstractArray{Quantity{T1,D,U1}},
         y::AbstractArray{Quantity{T2,D,U2}}; rtol::Real=Base.rtoldefault(T1,T2),
diff --git a/test/runtests.jl b/test/runtests.jl
index 07a79834..9bd03c64 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -394,6 +394,11 @@ end
         @test frexp(1.5m) == (0.75m, 1.0)
         @test unit(nextfloat(0.0m)) == m
         @test unit(prevfloat(0.0m)) == m
+
+        @test isapprox(1.0u"m", 1.1u"m"; atol=0.2u"m")
+        @test !isapprox(1.0u"m", 1.1u"m"; atol=0.05u"m")
+        @test isapprox(1.0u"m", 1.1u"m"; rtol=0.2)
+        @test !isapprox(1.0u"m", 1.1u"m"; rtol=0.05)
     end
 
     @testset "> fastmath" begin