diff --git a/src/contexts/init.jl b/src/contexts/init.jl
index 4baca1b57..aee561896 100644
--- a/src/contexts/init.jl
+++ b/src/contexts/init.jl
@@ -94,13 +94,11 @@ struct InitFromParams{P,S<:Union{AbstractInitStrategy,Nothing}} <: AbstractInitS
     params::P
     fallback::S
     function InitFromParams(
-        params::AbstractDict{<:VarName}, fallback::Union{AbstractInitStrategy,Nothing}
+        params::AbstractDict{<:VarName},
+        fallback::Union{AbstractInitStrategy,Nothing}=InitFromPrior(),
     )
         return new{typeof(params),typeof(fallback)}(params, fallback)
     end
-    function InitFromParams(params::AbstractDict{<:VarName})
-        return InitFromParams(params, InitFromPrior())
-    end
     function InitFromParams(
         params::NamedTuple, fallback::Union{AbstractInitStrategy,Nothing}=InitFromPrior()
     )
diff --git a/src/sampler.jl b/src/sampler.jl
index ed1b86321..4cc56d8ff 100644
--- a/src/sampler.jl
+++ b/src/sampler.jl
@@ -53,6 +53,25 @@ sampling with `sampler`. Defaults to `InitFromPrior()`, but can be overridden.
 """
 init_strategy(::AbstractSampler) = InitFromPrior()
 
+"""
+    _convert_initial_params(initial_params)
+
+Convert `initial_params` to an `AbstractInitStrategy` if it is not already one.
+"""
+_convert_initial_params(initial_params::AbstractInitStrategy) = initial_params
+function _convert_initial_params(nt::NamedTuple)
+    @info "Using a NamedTuple for `initial_params` will be deprecated in a future release. Please use `InitFromParams(namedtuple)` instead."
+    return InitFromParams(nt)
+end
+function _convert_initial_params(d::AbstractDict{<:VarName})
+    @info "Using a Dict for `initial_params` will be deprecated in a future release. Please use `InitFromParams(dict)` instead."
+    return InitFromParams(d)
+end
+function _convert_initial_params(::AbstractVector)
+    errmsg = "`initial_params` must be a `NamedTuple`, an `AbstractDict{<:VarName}`, or ideally an `AbstractInitStrategy`. Using a vector of parameters for `initial_params` is no longer supported. Please see https://turinglang.org/docs/usage/sampling-options/#specifying-initial-parameters for details on how to update your code."
+    throw(ArgumentError(errmsg))
+end
+
 function AbstractMCMC.sample(
     rng::Random.AbstractRNG,
     model::Model,
@@ -63,7 +82,13 @@ function AbstractMCMC.sample(
     kwargs...,
 )
     return AbstractMCMC.mcmcsample(
-        rng, model, sampler, N; initial_params, initial_state, kwargs...
+        rng,
+        model,
+        sampler,
+        N;
+        initial_params=_convert_initial_params(initial_params),
+        initial_state,
+        kwargs...,
     )
 end
 
@@ -79,7 +104,15 @@ function AbstractMCMC.sample(
     kwargs...,
 )
     return AbstractMCMC.mcmcsample(
-        rng, model, sampler, parallel, N, nchains; initial_params, initial_state, kwargs...
+        rng,
+        model,
+        sampler,
+        parallel,
+        N,
+        nchains;
+        initial_params=map(_convert_initial_params, initial_params),
+        initial_state,
+        kwargs...,
     )
 end
 
diff --git a/test/sampler.jl b/test/sampler.jl
index 8be54901d..3fe7f2b07 100644
--- a/test/sampler.jl
+++ b/test/sampler.jl
@@ -138,6 +138,14 @@
                 end
             end
 
+            # check that Vector no longer works
+            @test_throws ArgumentError sample(
+                model, sampler, 1; initial_params=[4, -1], progress=false
+            )
+            @test_throws ArgumentError sample(
+                model, sampler, 1; initial_params=[missing, -1], progress=false
+            )
+
             # model with two variables: initialization s = 4, m = -1
             @model function twovars()
                 s ~ InverseGamma(2, 3)
@@ -145,7 +153,12 @@
             end
             model = twovars()
             lptrue = logpdf(InverseGamma(2, 3), 4) + logpdf(Normal(0, 2), -1)
-            let inits = InitFromParams((; s=4, m=-1))
+            for inits in (
+                InitFromParams((s=4, m=-1)),
+                (s=4, m=-1),
+                InitFromParams(Dict(@varname(s) => 4, @varname(m) => -1)),
+                Dict(@varname(s) => 4, @varname(m) => -1),
+            )
                 chain = sample(model, sampler, 1; initial_params=inits, progress=false)
                 @test chain[1].metadata.s.vals == [4]
                 @test chain[1].metadata.m.vals == [-1]
@@ -169,7 +182,16 @@
             end
 
             # set only m = -1
-            for inits in (InitFromParams((; s=missing, m=-1)), InitFromParams((; m=-1)))
+            for inits in (
+                InitFromParams((; s=missing, m=-1)),
+                InitFromParams(Dict(@varname(s) => missing, @varname(m) => -1)),
+                (; s=missing, m=-1),
+                Dict(@varname(s) => missing, @varname(m) => -1),
+                InitFromParams((; m=-1)),
+                InitFromParams(Dict(@varname(m) => -1)),
+                (; m=-1),
+                Dict(@varname(m) => -1),
+            )
                 chain = sample(model, sampler, 1; initial_params=inits, progress=false)
                 @test !ismissing(chain[1].metadata.s.vals[1])
                 @test chain[1].metadata.m.vals == [-1]