diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index c76bf09f..16cae3ba 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -97,7 +97,7 @@ jobs:
       # TODO: use quarto_jll for integration tests once modern enough versions are available
       - uses: quarto-dev/quarto-actions/setup@9e48da27e184aa238fcb49f5db75469626d43adb # v2.1.9
         with:
-          version: 1.7.17
+          version: 1.7.34
 
       - uses: julia-actions/julia-buildpkg@e3eb439fad4f9aba7da2667e7510e4a46ebc46e1 # v1.7.0
       - uses: julia-actions/julia-runtest@678da69444cd5f13d7e674a90cb4f534639a14f9 # v1.11.2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad358395..f904335e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   explicitly in the notebook process [#306].
 - Contributing guidelines with AI assistance policy and AGENTS.md for AI coding assistants [#335].
 
+### Fixed
+
+- Refresh `QUARTO_PROJECT_ROOT` environment variable when rendering multiple projects sequentially [#336].
+
 ## [v0.17.3] - 2025-05-19
 
 ### Fixed
@@ -468,3 +472,4 @@ caching is enabled. Delete this folder to clear the cache. [#259]
 [#305]: https://github.com/PumasAI/QuartoNotebookRunner.jl/issues/305
 [#306]: https://github.com/PumasAI/QuartoNotebookRunner.jl/issues/306
 [#335]: https://github.com/PumasAI/QuartoNotebookRunner.jl/issues/335
+[#336]: https://github.com/PumasAI/QuartoNotebookRunner.jl/issues/336
diff --git a/src/server.jl b/src/server.jl
index d0084d4d..5ce32c79 100644
--- a/src/server.jl
+++ b/src/server.jl
@@ -161,6 +161,14 @@ function _exeflags_and_env(options)
     # that the user has not set themselves to show up there.
     quarto_env = Base.byteenv(options["env"])
 
+    # Add QUARTO_PROJECT_ROOT if projectDir is provided in options.
+    # This ensures the environment variable is refreshed when rendering
+    # multiple projects sequentially.
+    project_dir = get(options, "projectDir", nothing)
+    if !isnothing(project_dir)
+        push!(quarto_env, "QUARTO_PROJECT_ROOT=$project_dir")
+    end
+
     # Ensure that coverage settings are passed to the worker so that worker
     # code is tracked correctly during tests.
     # Based on https://github.com/JuliaLang/julia/blob/eed18bdf706b7aab15b12f3ba0588e8fafcd4930/base/util.jl#L216-L229.
@@ -451,6 +459,7 @@ function _extract_relevant_options(file_frontmatter::Dict, options::Dict)
     eval_default = get(get(D, file_frontmatter, "execute"), "eval", true)
     daemon_default = get(get(D, file_frontmatter, "execute"), "daemon", true)
     cache_default = get(get(D, file_frontmatter, "execute"), "cache", false)
+    project_dir_default = get(file_frontmatter, "projectDir", nothing)
 
     pandoc_to_default = nothing
 
@@ -472,6 +481,7 @@ function _extract_relevant_options(file_frontmatter::Dict, options::Dict)
             params = params_default,
             cache = cache_default,
             env = Dict{String,Any}(),
+            project_dir = project_dir_default,
         )
     else
         format = get(D, options, "format")
@@ -485,6 +495,7 @@ function _extract_relevant_options(file_frontmatter::Dict, options::Dict)
         eval = get(execute, "eval", eval_default)
         daemon = get(execute, "daemon", daemon_default)
         cache = get(execute, "cache", cache_default)
+        project_dir = get(options, "projectDir", nothing)
 
         pandoc = get(D, format, "pandoc")
         pandoc_to = get(pandoc, "to", pandoc_to_default)
@@ -514,6 +525,7 @@ function _extract_relevant_options(file_frontmatter::Dict, options::Dict)
             params = params_merged,
             cache,
             env,
+            project_dir,
         )
     end
 end
@@ -531,6 +543,7 @@ function _options_template(;
     params,
     cache,
     env,
+    project_dir,
 )
     D = Dict{String,Any}
     return D(
@@ -550,6 +563,7 @@ function _options_template(;
         ),
         "params" => D(params),
         "env" => env,
+        "projectDir" => project_dir,
     )
 end
 
diff --git a/test/examples/quarto_integration/projectA/_quarto.yml b/test/examples/quarto_integration/projectA/_quarto.yml
new file mode 100644
index 00000000..e69de29b
diff --git a/test/examples/quarto_integration/projectA/projectA.qmd b/test/examples/quarto_integration/projectA/projectA.qmd
new file mode 100644
index 00000000..aab42874
--- /dev/null
+++ b/test/examples/quarto_integration/projectA/projectA.qmd
@@ -0,0 +1,7 @@
+---
+engine: julia
+---
+
+```{julia}
+@show ENV["QUARTO_PROJECT_ROOT"]
+```
diff --git a/test/examples/quarto_integration/projectB/_quarto.yml b/test/examples/quarto_integration/projectB/_quarto.yml
new file mode 100644
index 00000000..e69de29b
diff --git a/test/examples/quarto_integration/projectB/projectB.qmd b/test/examples/quarto_integration/projectB/projectB.qmd
new file mode 100644
index 00000000..aab42874
--- /dev/null
+++ b/test/examples/quarto_integration/projectB/projectB.qmd
@@ -0,0 +1,7 @@
+---
+engine: julia
+---
+
+```{julia}
+@show ENV["QUARTO_PROJECT_ROOT"]
+```
diff --git a/test/testsets/quarto_integration/projectdir.jl b/test/testsets/quarto_integration/projectdir.jl
new file mode 100644
index 00000000..47df8af8
--- /dev/null
+++ b/test/testsets/quarto_integration/projectdir.jl
@@ -0,0 +1,35 @@
+include("../../utilities/prelude.jl")
+
+@testset "quarto project root env variable" begin
+    dir = joinpath(@__DIR__, "..", "..", "examples", "quarto_integration")
+    file_a = joinpath(dir, "projectA", "projectA.qmd")
+    file_b = joinpath(dir, "projectB", "projectB.qmd")
+    # TODO: use quarto_jll for integration tests once modern enough versions are available
+    cmd(file) = addenv(
+        `quarto render $file --to md`,
+        "QUARTO_JULIA_PROJECT" => normpath(joinpath(@__DIR__, "..", "..", "..")),
+    )
+
+    function server_start_time_and_pid()
+        status = readchomp(`quarto call engine julia status`)
+        started_at = something(match(r"started at: ([\d\:]+)", status))[1]
+        pid = something(match(r"pid: (\d+)", status))[1]
+        return started_at, pid
+    end
+
+    run(cmd(file_a))
+    time_pid_a = server_start_time_and_pid()
+    run(cmd(file_b))
+    time_pid_b = server_start_time_and_pid()
+
+    # make sure server process hasn't changed so the env variable
+    # can't have been updated this way
+    @test time_pid_a == time_pid_b
+
+    outputfile_a = joinpath(dir, "projectA", "projectA.md")
+    outputfile_b = joinpath(dir, "projectB", "projectB.md")
+    @test occursin(r"QUARTO_PROJECT_ROOT.*?projectA", read(outputfile_a, String))
+    @test occursin(r"QUARTO_PROJECT_ROOT.*?projectB", read(outputfile_b, String))
+    rm(outputfile_a)
+    rm(outputfile_b)
+end