diff --git a/lib/ModelingToolkitBase/src/systems/system.jl b/lib/ModelingToolkitBase/src/systems/system.jl
index ee88081e13..ca7aafc2fe 100644
--- a/lib/ModelingToolkitBase/src/systems/system.jl
+++ b/lib/ModelingToolkitBase/src/systems/system.jl
@@ -398,6 +398,7 @@ end
 
 defsdict(x::SymmapT) = x
 defsdict(x::Vector{Any}) = isempty(x) ? SymmapT() : defsdict(Dict(x))
+
 function defsdict(x::Union{AbstractDict, AbstractArray{<:Pair}})
     result = SymmapT()
     for (k, v) in x
@@ -406,6 +407,20 @@ function defsdict(x::Union{AbstractDict, AbstractArray{<:Pair}})
     return result
 end
 
+function defsdict(
+        x::Union{AbstractDict, AbstractArray{<:Pair}}, var_to_name::Dict{Symbol, SymbolicT}
+    )
+    result = SymmapT()
+    for (k, v) in x
+        k_unwrapped = unwrap(k)
+        if k_unwrapped isa Symbol
+            k_unwrapped = get(var_to_name, k_unwrapped, k_unwrapped)
+        end
+        result[k_unwrapped] = SU.Const{VartypeT}(v)
+    end
+    return result
+end
+
 as_atomicmap(::Type{T}, x::AtomicMapT{T}) where {T} = x
 function as_atomicmap(::Type{T}, x::Union{AbstractDict, AbstractArray{<:Pair}}) where {T}
     result = AtomicMapT{T}()
@@ -517,9 +532,12 @@ function System(
     end
     var_to_name = Dict{Symbol, SymbolicT}()
 
-    bindings = defsdict(bindings)
-    initial_conditions = defsdict(initial_conditions)
-    guesses = defsdict(guesses)
+    # Populate var_to_name early so defsdict can resolve Symbol keys (e.g. :X => 1.0)
+    collect_var_to_name!(var_to_name, dvs)
+    collect_var_to_name!(var_to_name, ps)
+    bindings = defsdict(bindings, var_to_name)
+    initial_conditions = defsdict(initial_conditions, var_to_name)
+    guesses = defsdict(guesses, var_to_name)
     all_dvs = as_atomic_array_set(dvs)
     if iv === nothing
         for k in keys(bindings)
diff --git a/lib/ModelingToolkitBase/test/binding_semantics.jl b/lib/ModelingToolkitBase/test/binding_semantics.jl
index 3590d05ce2..fb5aec5942 100644
--- a/lib/ModelingToolkitBase/test/binding_semantics.jl
+++ b/lib/ModelingToolkitBase/test/binding_semantics.jl
@@ -112,3 +112,15 @@ end
     @parameters p::Int q::String
     @test_throws "only valid for solvable" System(Equation[], t, [], [q]; bindings = [q => missing], name = :a)
 end
+
+@testset "Symbol keys in initial_conditions, guesses, and bindings" begin
+    @variables x(t)
+    @parameters p d
+    eqs = [D(x) ~ p - d * x]
+
+    sys = System(eqs, t; initial_conditions = [:x => 1.0, :p => 2.0],
+        guesses = [:x => 0.5], bindings = [:d => 2p], name = :a)
+    @test isequal(initial_conditions(sys), Dict(x => SConst(1.0), p => SConst(2.0)))
+    @test isequal(guesses(sys), Dict(x => SConst(0.5)))
+    @test isequal(bindings(sys), Dict(d => 2p))
+end